[ios blink] Make webnn work on the device

tflite as a fallback works correctly on iOS in the GPU process.
CoreML model requires file system access to compile a model
and the GPU process is restricted from having file access. We've
asked Apple to provide an update how CoreML can be used in the
sandboxed rendering process.

Bug: 40254930
Change-Id: I72598db882db38fa43d5d04f4c6055cbafb33a87
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6543648
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@google.com>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1460093}

services/webnn/BUILD.gn

@@ -106,7 +106,7 @@ component("webnn_service") {
     libs = [ "dxgi.lib" ]
   }
 
-  if (is_mac) {
+  if (is_apple) {
     sources += [
       "coreml/buffer_content_coreml.h",
       "coreml/buffer_content_coreml.mm",

services/webnn/coreml/graph_impl_coreml.mm

@@ -29,6 +29,7 @@
 #include "base/task/bind_post_task.h"
 #include "base/task/thread_pool.h"
 #include "base/types/expected_macros.h"
+#include "build/build_config.h"
 #include "mojo/public/cpp/base/big_buffer.h"
 #include "mojo/public/cpp/bindings/self_owned_associated_receiver.h"
 #include "services/webnn/coreml/buffer_content_coreml.h"
@@ -79,6 +80,7 @@ namespace {
 // compilation process.
 struct ScopedModelPaths {
   ~ScopedModelPaths() {
+#if BUILDFLAG(IS_MAC)
     if (base::CommandLine::ForCurrentProcess()->HasSwitch(
             switches::kWebNNCoreMlDumpModel)) {
       const auto dump_directory =
@@ -100,6 +102,7 @@ struct ScopedModelPaths {
         }
       }
     }
+#endif
     // Though the destructors of ScopedTempDir will delete these directories.
     // Explicitly delete them here to check for success.
     if (model_file_dir.IsValid()) {

services/webnn/features.gni

@@ -5,9 +5,11 @@
 import("//build/config/features.gni")
 import("//services/on_device_model/on_device_model.gni")
 
+assert(use_blink)
+
 declare_args() {
-  # TFLite is used as a fallback option on macOS and Windows.
-  webnn_use_tflite = is_android || is_chromeos || is_linux || is_mac || is_win
+  # TFLite is used as a fallback option on Apple and Windows.
+  webnn_use_tflite = is_android || is_chromeos || is_linux || is_apple || is_win
 
   # Enable the GPU delegate provided by the Optimization Guide library.
   webnn_use_chrome_ml_api = enable_ml_internal

services/webnn/public/mojom/features.mojom

@@ -18,10 +18,19 @@ feature kExperimentalWebMachineLearningNeuralNetwork {
 };
 
 // Enables the Core ML backend for WebNN.
-[EnableIf=is_mac]
+[EnableIf=is_apple]
 feature kWebNNCoreML {
   const string name = "WebNNCoreML";
+
+  // macOS default state is enabled.
+  [EnableIf=is_macos]
   const bool default_state = true;
+
+  // iOS default state is disabled since there are sandbox issues
+  // with using CoreML in the GPU process, we are waiting to hear back
+  // from Apple. https://crbug.com/417496826
+  [EnableIf=is_ios]
+  const bool default_state = false;
 };
 
 // Enables the DirectML backend for WebNN.

services/webnn/webnn_context_provider_impl.cc

@@ -24,6 +24,9 @@
 
 #if BUILDFLAG(IS_MAC)
 #include "base/mac/mac_util.h"
+#endif
+
+#if BUILDFLAG(IS_APPLE)
 #include "services/webnn/coreml/context_impl_coreml.h"
 #endif
 
@@ -187,15 +190,18 @@ void WebNNContextProviderImpl::CreateWebNNContext(
   }
 #endif  // BUILDFLAG(IS_WIN)
 
-#if BUILDFLAG(IS_MAC)
+#if BUILDFLAG(IS_APPLE)
   if (__builtin_available(macOS 14, *)) {
-    if (base::FeatureList::IsEnabled(mojom::features::kWebNNCoreML) &&
-        base::mac::GetCPUType() == base::mac::CPUType::kArm) {
+    if (base::FeatureList::IsEnabled(mojom::features::kWebNNCoreML)
+#if BUILDFLAG(IS_MAC)
+        && base::mac::GetCPUType() == base::mac::CPUType::kArm
+#endif  // BUILDFLAG(IS_MAC)
+    ) {
       context_impl = std::make_unique<coreml::ContextImplCoreml>(
           std::move(receiver), this, std::move(options));
     }
   }
-#endif  // BUILDFLAG(IS_MAC)
+#endif  // BUILDFLAG(IS_APPLE)
 
 #if BUILDFLAG(WEBNN_USE_TFLITE)
   if (!context_impl) {