Introduce a new WebAPK launch action.

chrome/android/java/AndroidManifest.xml

Index: chrome/android/java/AndroidManifest.xml
diff --git a/chrome/android/java/AndroidManifest.xml b/chrome/android/java/AndroidManifest.xml
index 464c9825e32fbe0ddff9ca803a5e15389b380faa..c2bed8d3327734aa13525e7029f2750128ae4bbf 100644
--- a/chrome/android/java/AndroidManifest.xml
+++ b/chrome/android/java/AndroidManifest.xml
@@ -481,6 +481,10 @@ by a child template that "extends" this file.
                 <action android:name="com.google.android.apps.chrome.webapps.WebappManager.ACTION_START_WEBAPP" />
                 <category android:name="android.intent.category.DEFAULT" />
             </intent-filter>
+            <intent-filter>
+                <action android:name="org.chromium.webapk.ACTION_START_WEBAPK" />

[Yaron, 2017/06/27 14:38:24]

wdyt about omitting "chromium" this time? Or I take it you want to keep
consistent with our package names? If so, I"m ok with it.

[Xi Han, 2017/06/27 15:05:49]

I don't have a strong preference between "org.chromium.webapk" and
"android.intent", and I am open to suggestions:)

[Yaron, 2017/06/27 15:19:41]

In the doc (#5), we selected org.webapk.ACTION_START_WEBAPK. Shall we go with
that? I could also see us renaming this to ACTION_START_WEBAPP /
ACTION_START_PWA but maybe it's ok to mention the specific implementation tech
because it affects our expectations. +Dom for general installability thoughts.
FTR I think org.webapk.ACTION_START_WEBAPK is fine, just want to give him a
chance to chime in :)

[Xi Han, 2017/06/27 17:37:17]

I am fine with "org.webapk.ACTION_START_WEBAPK" too. Let's see how Dom feels:)

+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
         </activity>
         <activity-alias android:name="com.google.android.apps.chrome.webapps.WebappManager"
             android:targetActivity="org.chromium.chrome.browser.webapps.WebappLauncherActivity">