Building the Chromium-based WebView in AOSP is no longer supported or required.
WebView can now be built entirely from the Chromium source code.

Docs on how to build WebView from Chromium for use in AOSP are available here:
https://chromium.googlesource.com/chromium/src/+/HEAD/android_webview/docs/aosp-system-integration.md

For questions about building WebView, please contact our mailing list:
https://groups.google.com/a/chromium.org/forum/#!forum/android-webview-dev

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The prebuilt APKs provided here are built from Chromium upstream sources; you
should check the commit message to see the version number for a particular
prebuilt. The version number is formatted like "12.0.3456.789" and matches the
tag in the Chromium repository it was built from.

If you want to build your own WebView, you should generally build the latest
stable version, not the version published here: newer versions have important
security and stability improvements.


General instructions for building WebView from Chromium:
https://www.chromium.org/developers/how-tos/build-instructions-android-webview

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The prebuilt libwebviewchromium.so included in these APKs is built from Chromium
release, using the GN build tool. To match our build settings, set:

target_os = "android"
is_debug = false
is_official_build = true
is_chrome_branded = false
use_official_google_api_keys = false
ffmpeg_branding = "Chrome"
proprietary_codecs = true
enable_resource_whitelist_generation = false
enable_remoting = true
is_component_build = false
symbol_level = 0
enable_nacl = false
blink_symbol_level = 0
webview_devui_show_icon = false
android_default_version_name = "84.0.4147.89"
android_default_version_code = "4147089$$"

$$ depends on device ARCH
(00=arm, 50=arm64, 10=x86, 60=x64)

in your GN argument file before building.

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Replace webview icon:

From the chromium/src directory:

mkdir -p android_webview/apk/java/res/drawable-xxxhdpi
cp chrome/android/java/res_chromium/mipmap-mdpi/app_icon.png android_webview/apk/java/res/drawable-mdpi/icon_webview.png
cp chrome/android/java/res_chromium/mipmap-hdpi/app_icon.png android_webview/apk/java/res/drawable-hdpi/icon_webview.png
cp chrome/android/java/res_chromium/mipmap-xhdpi/app_icon.png android_webview/apk/java/res/drawable-xhdpi/icon_webview.png
cp chrome/android/java/res_chromium/mipmap-xxhdpi/app_icon.png android_webview/apk/java/res/drawable-xxhdpi/icon_webview.png
cp chrome/android/java/res_chromium/mipmap-xxxhdpi/app_icon.png android_webview/apk/java/res/drawable-xxxhdpi/icon_webview.png

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For questions about building WebView, please see
https://groups.google.com/a/chromium.org/forum/#!forum/android-webview-dev