AW: add a GN arg for shell package name

No change to production logic, only test shell.

This adds 'system_webview_shell_package_name' to configure WebView
shell's package name. This is handy for Android emulators, because the
default package name will cause signature mismatches.

I kept the original documentation (for removing the shell from the
system image) because it may be relevant for some use cases. But I hope
the GN arg is a simpler solution for most developers.

Fixed: 1061211
Test: $OUT/bin/system_webview_shell_apk package-info (verify name)
Test: $OUT/bin/system_webview_shell_apk install (succeeds on emulator)
Test: Upload to gerrit > open file > click "gitiles" > verify markdown
Change-Id: I24a35524bc5042da33b8203637ec67a0f610f363
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2101859Reviewed-by: Hazem Ashmawy <hazems@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750249}

android_webview/docs/webview-shell.md

@@ -20,6 +20,38 @@ at the top. This can be helpful for checking which WebView version is installed
 & selected on the device.
 ***
 
+## Setting up the build
+
+The bare minimum GN args is just `target_os = "android"`. It's simplest to just
+reuse the same out/ folder you use for WebView or Chrome for Android.
+
+If you're building for an emulator, be aware WebView shell is preinstalled with
+a different signing key. If you just need a WebView app, the preinstalled
+WebView shell may be sufficient (and you don't need to build your own).
+
+If you want a more up-to-date WebView shell or you want to use the convenience
+scripts in this guide (ex. `.../system_webview_shell_apk launch <url>`), then
+you can workaround the signature mismatch by changing your local WebView shell's
+package name. Simply add the following to your GN args (run `gn args
+out/Default`):
+
+```gn
+# Change the package name to anything that won't conflict. If you're not sure
+# what to use, here's a safe choice:
+system_webview_shell_package_name = "org.chromium.my_webview_shell"
+```
+
+This will let your local build install alongside the preinstalled WebView shell.
+If you'd like, you can disable the preinstalled shell to avoid confusing the two
+apps. In a terminal:
+
+```sh
+$ adb root
+# Make sure to specify the default package name ("org.chromium.webview_shell"),
+# not the one you used in the GN args above!
+$ adb shell pm disable org.chromium.webview_shell
+```
+
 ## Building the shell
 
 ```sh
@@ -33,18 +65,31 @@ $ autoninja -C out/Default system_webview_shell_apk
 $ out/Default/bin/system_webview_shell_apk install
 ```
 
-The WebView shell may be preinstalled on a device or emulator. If the signature
-of the locally built shell does not match the preinstalled shell then the
-install will fail &ndash; usually with this error:
+## Running the shell
 
+```sh
+# Launch a URL from the commandline, or open the app from the app launcher
+$ out/Default/bin/system_webview_shell_apk launch "https://www.google.com/"
+
+# For more commands:
+$ out/Default/bin/system_webview_shell_apk --help
 ```
-...
-path/to/SystemWebViewShell.apk: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE:
-Package org.chromium.webview_shell signatures do not match previously installed
-version; ignoring!]
-```
 
-If this occurs then delete the preinstalled WebView shell as so:
+*** note
+**Note:** `system_webview_shell_apk` does not support modifying CLI flags. See
+https://crbug.com/959425. Instead, you should modify WebView's flags by
+following [commandline-flags.md](./commandline-flags.md).
+***
+
+## Troubleshooting
+
+### INSTALL\_FAILED\_UPDATE\_INCOMPATIBLE: Package ... signatures do not match previously installed version
+
+The easiest way to workaround this is to [change the shell's package name in a
+local build](#building-for-the-emulator).
+
+If you **need** to use the same package name (ex. you're installing an official
+build of WebView shell), then you can modify the system image.
 
 *** note
 **Note:** If using the emulator ensure it is being started with the
@@ -66,19 +111,3 @@ $ adb shell rm /system/app/Browser2/Browser2.apk
 $ adb shell stop
 $ adb shell start
 ```
-
-## Running the shell
-
-```sh
-# Launch a URL from the commandline, or open the app from the app launcher
-$ out/Default/bin/system_webview_shell_apk launch "https://www.google.com/"
-
-# For more commands:
-$ out/Default/bin/system_webview_shell_apk --help
-```
-
-*** note
-**Note:** `system_webview_shell_apk` does not support modifying CLI flags. See
-https://crbug.com/959425. Instead, you should modify WebView's flags by
-following [commandline-flags.md](./commandline-flags.md).
-***

android_webview/tools/system_webview_shell/BUILD.gn

@@ -16,6 +16,17 @@ group("system_webview_shell") {
   ]
 }
 
+declare_args() {
+  # Android package name to use for system_webview_shell_apk (the WebView shell
+  # browser). You can change this package name to work around signing key
+  # conflicts (INSTALL_FAILED_UPDATE_INCOMPATIBLE) on devices/emulators which
+  # have the shell browser preinstalled under the default package name.
+  system_webview_shell_package_name = "org.chromium.webview_shell"
+}
+
+system_webview_shell_android_manifest =
+    "$root_gen_dir/android_webview/system_webview_shell_apk/AndroidManifest.xml"
+
 android_apk("system_webview_shell_apk") {
   apk_name = "SystemWebViewShell"
   sources = [
@@ -35,7 +46,8 @@ android_apk("system_webview_shell_apk") {
     "apk/src/org/chromium/webview_shell/WebViewTracingActivity.java",
     "apk/src/org/chromium/webview_shell/WebViewWithClipPath.java",
   ]
-  android_manifest = "apk/AndroidManifest.xml"
+  android_manifest = system_webview_shell_android_manifest
+  android_manifest_dep = ":system_webview_shell_manifest"
   target_sdk_version = 29
   deps = [
     ":system_webview_shell_apk_resources",
@@ -45,6 +57,12 @@ android_apk("system_webview_shell_apk") {
   ]
 }
 
+jinja_template("system_webview_shell_manifest") {
+  input = "apk/AndroidManifest.xml"
+  output = system_webview_shell_android_manifest
+  variables = [ "manifest_package=$system_webview_shell_package_name" ]
+}
+
 android_resources("system_webview_shell_apk_resources") {
   resource_dirs = [ "apk/res" ]
   custom_package = "org.chromium.webview_shell"

android_webview/tools/system_webview_shell/apk/AndroidManifest.xml

@@ -6,7 +6,7 @@
 
 <manifest
     xmlns:android="http://schemas.android.com/apk/res/android"
-    package="org.chromium.webview_shell"
+    package="{{manifest_package|default('org.chromium.webview_shell')}}"
     android:versionCode="1"
     android:versionName="1.0" >