Allow specifying maxSdkVersion for WebView.

Allow the jinja template parameters to specify a max SDK version for the
WebView APK. This will be used to handle special cases where we want the
Play Store's targeting to do something unusual.

Bug: 962672
Change-Id: I73940183e6c273831347d33e9b646cc4fb24e3ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610978
Auto-Submit: Richard Coles <torne@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Commit-Queue: Tobias Sargeant <tobiasjs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659438}

android_webview/apk/java/AndroidManifest.xml

@@ -10,7 +10,10 @@
     package="{{manifest_package|default('com.android.webview')}}"
     tools:ignore="MissingLeanbackLauncher">
     <uses-sdk android:minSdkVersion="{{min_sdk_version|default(21)}}"
-              android:targetSdkVersion="{{target_sdk_version|default(28)}}">
+              android:targetSdkVersion="{{target_sdk_version|default(28)}}"
+              {% if max_sdk_version is defined %}
+                android:maxSdkVersion="{{max_sdk_version}}"
+              {% endif %}>
     </uses-sdk>
 
     <uses-feature android:name="android.hardware.touchscreen"