Revert "Don't show video fullscreen until DidEnterFullscreen() is called, and disable fullscreen for non-media elements for android webview" (r177458).

Seems to be breaking android_webview_instrumentation_tests
AwContentsClientGetVideoLoadingProgressViewTest#testGetVideoLoadingProgressView

This reverts commit 3c62291af9ab9781c454868f6a9bf8a038c6ffda.

TBR=lushnikov,pilgrim@chromium.org
BUG=

Review URL: https://codereview.chromium.org/363323006

git-svn-id: svn://svn.chromium.org/blink/trunk@177498 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Follow up to r177450, do not .As() an empty handle.

Windows dbg and Windows Oilpan apparently doesn't allow empty handles
with .As(), which caused the webkit_unit_tests added in r177450 to
fail. Move the empty-handle check before the cast (turns out
ScriptPromise constructor casts anyway.)

BUG=363967

Review URL: https://codereview.chromium.org/364293003

git-svn-id: svn://svn.chromium.org/blink/trunk@177499 bbb929c8-8fbe-4397-9dbb-9b2b20218538