BrowserBookmarksAdapter does not need to request bookmark icons as most of the
bookmarks have up-to-date icons. We still need to request all icons on start up
because a new icon may be loaded as a result of clicking a history items.

Move the icon request to a background thread to not block the ui thread on large
db lookups.

Remove MostVisitedActivity as it is no longer used.

Bug: 2496872
Change-Id: I378dce8fdb7e825da96594cd31b720ea24758af1

Bug: #2361749.

Use the data from the java database before talking to the native database. The
bookmarks database may contain favicons that the native database does not have a
mapping for. Used the native icon database for recent history items since those
are not stored in the java db. Request the icons each time the activity is
created since the url->bitmap mapping is a global.

Merge commit 'b8a9cb0e2b3b2a1bb250853a79b8ea2046ff3d6e' into eclair

* commit 'b8a9cb0e2b3b2a1bb250853a79b8ea2046ff3d6e':
  Fix the activity leak in the Browser.

The IconListenerSet inside CombinedBookmarkHistoryActivity is static. So when
the activity is destroyed, it needs to remove its listener to avoid leak.

mUrlIndex, mTitleIndex, and mBookmarkIndex are member variables
which are the same for all MyAdapters, so change them to static.

and use <merge> instead of FrameLayout