android: Improve ActivityStatus and add ChromiumActivity.

The ActivityStatus class used to track activity state changes is too basic
for some usage scenarios.

This patch does the following:

- Augment ActivityStatus with a new StateListener type that can be
  registered to listen to all activity state changes.

  Also add getActivity(), getState(), registerStateListener()
  and unregisterStateListener() as static method.

- Add a new ChromiumActivity class that all Chromium main activities
  should sub-class, to ensure that the ActivityStatus state is updated
  appropriately.

- Modify all main activities in the Chromium code base to extend
  from ChromiumActivity instead of Activity.

BUG=none


Review URL: https://chromiumcodereview.appspot.com/11419287

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171789 0039d316-1c4b-4281-b951-d872f2087c98

• base/android/java/src/org/chromium/base/ActivityStatus.java[diff]
• base/android/java/src/org/chromium/base/ChromiumActivity.java[Added - diff]
• chrome/android/testshell/java/src/org/chromium/chrome/testshell/ChromiumTestShellActivity.java[diff]
• content/public/android/java/src/org/chromium/content/browser/LocationProvider.java[diff]
• content/public/android/javatests/src/org/chromium/content/browser/LocationProviderTest.java[diff]
• content/shell/android/java/src/org/chromium/content_shell/ContentShellActivity.java[diff]
• net/android/java/src/org/chromium/net/NetworkChangeNotifierAutoDetect.java[diff]
• testing/android/java/src/org/chromium/native_test/ChromeNativeTestActivity.java[diff]