Make Android back work correctly in Elderberry.

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 30de1075395550cd098f7460f56775779417c421..502ea38462635fed5b93ac67798a03e41978afa0 100644
--- a/chrome/android/java/AndroidManifest.xml
+++ b/chrome/android/java/AndroidManifest.xml
@@ -138,7 +138,9 @@ by a child template that "extends" this file.
              do not specify one here to allow it to inherit from the app. -->
         <activity android:name="org.chromium.chrome.browser.document.ChromeLauncherActivity"
             android:theme="@android:style/Theme.Translucent.NoTitleBar"
-            android:relinquishTaskIdentity="true">
+            android:relinquishTaskIdentity="true"
+            android:taskAffinity=""

[Maria, 2016/06/17 22:35:51]

The only thing I don't understand is why this doesn't separate regular
CustomTabActivity into a new task stack. Is it because of
relinquishTaskIdentity?

[Ted C, 2016/06/20 15:49:16]

That was only added in Lollipop, so it can't be that.  I wish I knew :-/

+            android:excludeFromRecents="true">
         </activity>
         <activity-alias android:name="com.google.android.apps.chrome.Main"
             android:targetActivity="org.chromium.chrome.browser.document.ChromeLauncherActivity"
@@ -281,18 +283,16 @@ by a child template that "extends" this file.
 
         <!-- ChromeTabbedActivity related -->
         <activity android:name="org.chromium.chrome.browser.ChromeTabbedActivity"
-             android:theme="@style/MainTheme"
+             android:theme="@style/TabbedModeTheme"
              android:exported="false"
-             android:windowBackground="@drawable/window_background"
              android:windowSoftInputMode="adjustResize"
              android:launchMode="singleTask"
              android:configChanges="orientation|keyboardHidden|keyboard|screenSize|mcc|mnc|screenLayout|smallestScreenSize"
              android:hardwareAccelerated="false">
         </activity>
         <activity android:name="org.chromium.chrome.browser.ChromeTabbedActivity2"
-             android:theme="@style/MainTheme"
+             android:theme="@style/TabbedModeTheme"
              android:exported="false"
-             android:windowBackground="@drawable/window_background"
              android:windowSoftInputMode="adjustResize"
              android:taskAffinity="{{ manifest_package }}.ChromeTabbedActivity2"
              android:launchMode="singleTask"
@@ -300,9 +300,8 @@ by a child template that "extends" this file.
              android:hardwareAccelerated="false">
         </activity>
         <activity android:name="org.chromium.chrome.browser.multiwindow.MultiInstanceChromeTabbedActivity"
-            android:theme="@style/MainTheme"
+            android:theme="@style/TabbedModeTheme"
             android:exported="false"
-            android:windowBackground="@drawable/window_background"
             android:windowSoftInputMode="adjustResize"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|mcc|mnc|screenLayout|smallestScreenSize"
             android:hardwareAccelerated="false">