Update safe_browsing code to use WebElementCollection instead of WebNodeCollection

Update safe_browsing code to use WebElementCollection instead of WebNodeCollection.
After Blink r166411 and r166500, WebNodeCollection is renamed to
WebElementCollection and its API returns WebElements instead of WebNodes.

The new code is clearer and avoids unnecessary isElementNode() checks.

Review URL: https://codereview.chromium.org/146053007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249720 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249720
Simple Telemetry benchmark for WebRTC

Adds a benchmark that performs CPU and memory
measurements on a simple page only showing the
video stream from a local fake video device in 
a video tag.

BUG=333257
TEST=Compiled Chrome in Release mode. Ran:
tools/perf/run_benchmark --browser=release webrtc

Review URL: https://codereview.chromium.org/133733003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249721 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249721