Open more file types in Chrome, and audit the dangerous file extensions.

Re-order the extensions list to make more sense, and unify some duplicate
extensions.

Resolve the TODO(cevans) by (a) noting that our per-file origin separation
is good enough now; and (b) by opening those file types in Chrome.

BUG=320126,323561

Review URL: https://codereview.chromium.org/106953003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239325 0039d316-1c4b-4281-b951-d872f2087c98
cc: Add histogram for unserviced copy requests and return by reference.

The LayerTreeImpl::LayersWithCopyOutputRequest() method is returning
a const std::vector<> instead of a const std::vector<>&. Oops.

But for this to be a huge perf problem, we must have a large vector
somehow. So adding a UMA histogram to tell us if the browser
is doing awful things and requesting a whole lot of copy requests
on undrawable subtrees.

R=enne
BUG=326617

Review URL: https://codereview.chromium.org/108853004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239326 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239326
Telemetry: Fix typo in LoadTimesTimelineMetric

BUG=321439

Review URL: https://codereview.chromium.org/108973002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239327 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239327