Remove WebMediaPlayerClient::setOpaque().

As of r264266 there are no more users of this API now that WebMediaPlayer implementations call WebLayerImpl::setOpaque() directly.

BUG=110814

Review URL: https://codereview.chromium.org/240253004

git-svn-id: svn://svn.chromium.org/blink/trunk@171896 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add a null check for importsForFrame()

There are chances that HTMLImportLoader::document() is null.
This change adds a check for that before using it in InspectorPageAgent.
This change also migrates cacheResourcesForFree() to use importsForFrame()
that we added the null check.

TEST=none
BUG=362425
R=dominicc@chromium.org, dglazkov@chromium.org

Review URL: https://codereview.chromium.org/235373006

git-svn-id: svn://svn.chromium.org/blink/trunk@171897 bbb929c8-8fbe-4397-9dbb-9b2b20218538