AW docs: clarify netlog and commandline flag requirements

No change to logic, only docs.

This clarifies that WebView requires debuggable Android images for all
commandline flags, including netlog. This repeats a code snippet for
checking if your device supports commandline flags.

Bug: 918221
Test: tools/md_browser/md_browser.py
Test: Upload to gerrit > open file > click "gitiles"
Change-Id: I03ebc095ee78744e9dfdbf9c113b418c57a53e7e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2029190
Reviewed-by: Shimi Zhang <ctzsm@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736640}

android_webview/docs/commandline-flags.md

@@ -1,13 +1,33 @@
 # Commandline flags
 
-## Applying flags
+## Can I apply commandline flags on my device?
 
 *** note
-**Note:** this requires either a `userdebug` or `eng` Android build (you can
+**Note:** WebView only permits toggling commandline flags on devices/emulators
-check with `adb shell getprop ro.build.type`). Flags cannot be enabled on
+running a debuggable Android OS image. **Most users cannot apply commandline
-production builds of Android.
+flags, because they're using devices with production Android images.**
 ***
 
+You can check which Android image you have on your device with the following:
+
+```sh
+# If you don't have `adb` in your path, you can source this file to use
+# the copy from chromium's Android SDK.
+$ source build/android/envsetup.sh
+
+# If this outputs "userdebug" or "eng" then you can apply flags following this
+# guide. If it outputs "user" then you cannot apply flags on this device.
+$ adb shell getprop ro.build.type
+userdebug
+```
+
+If the above outputs "user," then you **cannot** apply flags on the
+device/emulator. If you intend to use this device for chromium development, then
+you may consider [re-flashing the device or creating a debuggable Android
+emulator](device-setup.md).
+
+## Applying flags
+
 WebView reads flags from a specific file on the device as part of the startup
 sequence. Therefore, it's important to always **kill the WebView-based app**
 you're examining after modifying commandline flags, to ensure the flags are

android_webview/docs/device-setup.md

@@ -10,6 +10,22 @@ Android image.
 To build WebView, or [run WebView's automated tests](./test-instructions.md),
 you'll need to set up either an emulator or a physical device.
 
+## I have a device or emulator. Will it work for development?
+
+You can check which Android image you have on your device with the following:
+
+```sh
+# If you don't have `adb` in your path, you can source this file to use
+# the copy from chromium's Android SDK.
+$ source build/android/envsetup.sh
+
+# If this outputs "userdebug" or "eng" then you're OK! If this outputs "user"
+# then you must reflash your physical device or configure a new emulator
+# following this guide.
+$ adb shell getprop ro.build.type
+userdebug
+```
+
 ## Emulator (easy way)
 
 *** promo

android_webview/docs/net-debugging.md

@@ -5,15 +5,17 @@
 WebView supports the `kLogNetLog` flag to log debugging network info to a JSON
 file on disk.
 
-*** aside
+### Please do not request netlogs from reporters
-For more info on commandline flags, see
-[commandline-flags.md](./commandline-flags.md).
-***
 
 *** note
-**Note:** this requires either a `userdebug` or `eng` Android build (you can
+**Important**: at the moment, WebView netlog requires applying commandline
-check with `adb shell getprop ro.build.type`). Flags cannot be enabled on
+flags. **It's not typically possible for external reporters to apply commandline
-production builds of Android.
+flags, so please do not ask them to follow this guide.**
+
+This guide is only for chromium developers who are set up for WebView
+development. Specifically, this guide requires the reader to use a `userdebug`
+or `eng` Android image, see [device setup](device-setup.md) and [commandline
+flags](commandline-flags.md) for more information.
 ***
 
 ### Python script