Stop shipping v8 context snapshot for arm32

This introduces separate GN variables that are specific to the
secondary ABI so that the value of them can be known both to the
primary ABI (which needs to know whether or not to include them as
assets), as well as the secondary ABI (which needs to know the value
to pass to native code).

They are:
* use_v8_context_snapshot_secondary_abi
* include_both_v8_snapshots_secondary_abi

Which are compliments of:
* use_v8_context_snapshot
* include_both_v8_snapshots

This also makes v8_context_snapshot_filename a regular variable
rather than a GN args, since it seems unlikely that it is useful to
allow configuring this via GN args.

Bug: 377850453, 40539769
Change-Id: I882cb3d7540ea497ea3494a10f378a54d47724d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6011925
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1382620}

android_webview/expectations/trichrome_webview_64_32_bundle.arm64.libs_and_assets.expected

@@ -84,4 +84,3 @@ apk_path=assets/stored-locales/zh-CN.pak+com.android.webview+, compress=False, a
 apk_path=assets/stored-locales/zh-HK.pak+com.android.webview+, compress=False, alignment=4
 apk_path=assets/stored-locales/zh-TW.pak+com.android.webview+, compress=False, alignment=4
 apk_path=assets/stored-locales/zu.pak+com.android.webview+, compress=False, alignment=4
-apk_path=assets/v8_context_snapshot_32.bin+com.android.webview+, compress=False, alignment=4

chrome/android/expectations/monochrome_64_32_public_bundle.arm64.libs_and_assets.expected

@@ -170,7 +170,6 @@ apk_path=assets/stored-locales/zh-CN.pak, compress=False, alignment=4
 apk_path=assets/stored-locales/zh-HK.pak, compress=False, alignment=4
 apk_path=assets/stored-locales/zh-TW.pak, compress=False, alignment=4
 apk_path=assets/stored-locales/zu.pak, compress=False, alignment=4
-apk_path=assets/v8_context_snapshot_32.bin, compress=False, alignment=4
 apk_path=assets/v8_context_snapshot_64.bin, compress=False, alignment=4
 apk_path=assets/webapk8.dex, compress=True, alignment=0
 apk_path=assets/webapk_dex_version.txt, compress=True, alignment=0

chrome/android/expectations/trichrome_library_32_64_apk.arm64.libs_and_assets.expected

@@ -3,4 +3,3 @@ apk_path=lib/armeabi-v7a/libcrashpad_handler_trampoline.so, compress=False, alig
 apk_path=lib/armeabi-v7a/libmonochrome.so, compress=False, alignment=4096
 apk_path=assets/icudtl.dat+com.android.webview+, compress=False, alignment=4
 apk_path=assets/snapshot_blob_32.bin+com.android.webview+, compress=False, alignment=4
-apk_path=assets/v8_context_snapshot_32.bin+com.android.webview+, compress=False, alignment=4

chrome/android/expectations/trichrome_library_32_apk.arm64.libs_and_assets.expected

@@ -3,4 +3,3 @@ apk_path=lib/armeabi-v7a/libcrashpad_handler_trampoline.so, compress=False, alig
 apk_path=lib/armeabi-v7a/libmonochrome.so, compress=False, alignment=4096
 apk_path=assets/icudtl.dat+com.android.webview+, compress=False, alignment=4
 apk_path=assets/snapshot_blob_32.bin+com.android.webview+, compress=False, alignment=4
-apk_path=assets/v8_context_snapshot_32.bin+com.android.webview+, compress=False, alignment=4

gin/BUILD.gn

@@ -164,13 +164,14 @@ if (is_android && enable_java_templates &&
         disable_compression = true
         sources = []
         deps = []
-        if (use_v8_context_snapshot) {
+        if (use_v8_context_snapshot_secondary_abi) {
           sources += [ "$root_out_dir/v8_context_snapshot_32.bin" ]
           deps += [
             "//tools/v8_context_snapshot($android_secondary_abi_toolchain)",
           ]
         }
-        if (!use_v8_context_snapshot || include_both_v8_snapshots) {
+        if (!use_v8_context_snapshot_secondary_abi ||
+            include_both_v8_snapshots_secondary_abi) {
           _secondary_abi_out_dir =
               get_label_info("//v8($android_secondary_abi_toolchain)",
                              "root_out_dir")

tools/v8_context_snapshot/v8_context_snapshot.gni

@@ -13,46 +13,60 @@ import("//build/config/v8_target_cpu.gni")
 import("//v8/gni/v8.gni")
 
 declare_args() {
-  # If set, both snapshots are included. At this time, this only applicable to
-  # android. In other words, it will not work correctly on other platforms.
-  # Building the context snapshots on android requires building blink multiple
-  # times. To avoid impacting developer productivity the context snapshot is
-  # only built for official builds.
-  include_both_v8_snapshots =
-      is_official_build && target_os == "android" && v8_target_cpu == "arm64"
+  # Whether to include both snapshots on arm32 when building fat binary.
+  include_both_v8_snapshots_secondary_abi = false
 }
 
 declare_args() {
-  # TODO(crbug.com/40539769): Enable the feature on more environments.
-  # Disable in mac and win cross builds since building Blink twice is slow.
-  use_v8_context_snapshot =
-      include_both_v8_snapshots ||
-      (!is_chromeos && !is_android && !is_castos && !is_fuchsia &&
-       # Android may build for both 64 bit and 32bit. When this happens, the
-       # v8_target_cpu will not equal the target_cpu (for example,
-       # v8_target_cpu == "arm" but target_os == "arm64").
-       (v8_target_cpu == target_cpu || target_os == "android") &&
-       !(host_toolchain == default_toolchain && is_msan) &&
-       !(is_win && host_os != "win") && !(is_mac && host_os != "mac"))
-
-  # We use a different filename for arm64 macOS builds so that the arm64 and
-  # x64 snapshots can live side-by-side in a universal macOS app.
-  if (is_mac) {
-    if (v8_target_cpu == "x64") {
-      v8_context_snapshot_filename = "v8_context_snapshot.x86_64.bin"
-    } else if (v8_target_cpu == "arm64") {
-      v8_context_snapshot_filename = "v8_context_snapshot.arm64.bin"
-    }
-  } else if (target_os == "android") {
-    if (v8_current_cpu == "arm" || v8_current_cpu == "x86" ||
-        v8_current_cpu == "mipsel") {
-      v8_context_snapshot_filename = "v8_context_snapshot_32.bin"
-    } else {
-      v8_context_snapshot_filename = "v8_context_snapshot_64.bin"
-    }
+  # Android may build for both 64 bit and 32bit.
+  if (v8_current_cpu != v8_target_cpu) {
+    # If set, both snapshots are included. At this time, this only applicable to
+    # android. In other words, it will not work correctly on other platforms.
+    # Building the context snapshots on android requires building blink multiple
+    # times. To avoid impacting developer productivity the context snapshot is
+    # only built for official builds.
+    include_both_v8_snapshots = include_both_v8_snapshots_secondary_abi
   } else {
-    v8_context_snapshot_filename = "v8_context_snapshot.bin"
+    include_both_v8_snapshots =
+        is_official_build && target_os == "android" && target_cpu == "arm64"
   }
+
+  # Whether Android's secondary ABI should use the context snapshot.
+  use_v8_context_snapshot_secondary_abi =
+      include_both_v8_snapshots_secondary_abi
+}
+
+declare_args() {
+  if (v8_current_cpu != v8_target_cpu) {
+    # TODO(crbug.com/40539769): Enable the feature on more environments.
+    # Disable in mac and win cross builds since building Blink twice is slow.
+    use_v8_context_snapshot = use_v8_context_snapshot_secondary_abi
+  } else {
+    use_v8_context_snapshot =
+        include_both_v8_snapshots ||
+        (!is_chromeos && !is_android && !is_castos && !is_fuchsia &&
+         !(host_toolchain == default_toolchain && is_msan) &&
+         !(is_win && host_os != "win") && !(is_mac && host_os != "mac"))
+  }
+}
+
+# We use a different filename for arm64 macOS builds so that the arm64 and
+# x64 snapshots can live side-by-side in a universal macOS app.
+if (is_mac) {
+  if (v8_target_cpu == "x64") {
+    v8_context_snapshot_filename = "v8_context_snapshot.x86_64.bin"
+  } else if (v8_target_cpu == "arm64") {
+    v8_context_snapshot_filename = "v8_context_snapshot.arm64.bin"
+  }
+} else if (target_os == "android") {
+  if (v8_current_cpu == "arm" || v8_current_cpu == "x86" ||
+      v8_current_cpu == "mipsel") {
+    v8_context_snapshot_filename = "v8_context_snapshot_32.bin"
+  } else {
+    v8_context_snapshot_filename = "v8_context_snapshot_64.bin"
+  }
+} else {
+  v8_context_snapshot_filename = "v8_context_snapshot.bin"
 }
 
 # We cannot use V8 context snapshot, if V8 doesn't use snapshot files.