Added ScopedNSAutoreleasePool to RenderViewTest.

If Blink checks font metrics during some browser_test (e.g. PrintLayoutTest), Blink might allocates CFString by using Mac allocator, and the CFString might have a reference to StringImpl allocated by FastMalloc.

So we should invoke Mac decallocator before destroying Blink instance. If we don't, browser_tests will crash.

BUG=305885, 336756

Review URL: https://codereview.chromium.org/137023014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249043 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249043