Enable Browser Actions in dev and canary channel.

Enables Browser Actions related classes to be accessible in dev and
canary channel of Chrome.

BUG=None

Change-Id: I8c6f33b6bb8ad4451317c88ce4fcfec7b54f4545
Reviewed-on: https://chromium-review.googlesource.com/580698
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Lei Tian <ltian@google.com>
Cr-Commit-Position: refs/heads/master@{#489525}

chrome/android/java/AndroidManifest.xml

@@ -674,7 +674,7 @@ by a child template that "extends" this file.
         </activity>
 
         <!-- Activities for Browser Actions -->
-        {% if channel in ['default'] %}
+        {% if channel in ['dev', 'canary', 'default'] %}
         <activity android:name="org.chromium.chrome.browser.browseractions.BrowserActionActivity"
             android:theme="@style/FullscreenTransparentActivityTheme"
             android:exported="true"