Android Chromoting: Handle keyboard-related system config changes.

This prevents Bluetooth (and other external) keyboards from shutting
down the Desktop activity when activated or powered off.

BUG=471435

Review URL: https://codereview.chromium.org/1046503002

Cr-Commit-Position: refs/heads/master@{#322696}

remoting/android/java/AndroidManifest.xml.jinja2

@@ -36,7 +36,7 @@
             </intent-filter>
         </activity>
         <activity android:name="org.chromium.chromoting.Desktop"
-                android:configChanges="orientation|screenSize"
+                android:configChanges="orientation|screenSize|keyboard|keyboardHidden"
                 android:theme="@style/BaseTheme.Desktop"
                 android:windowSoftInputMode="adjustResize"/>
         <activity android:name="org.chromium.chromoting.HelpActivity"