Disable ctrl-click (and friends) prerender tests.

They currently prevent https://codereview.chromium.org/170703003/ from landing.
After that CL, until bug 345474 is fixed, they won't be testing anything at
all. Just disable them.

BUG=345474

Review URL: https://codereview.chromium.org/166833006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252475 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252475
[Telemetry] Only calculate tab contents bounding box once.

Cache it and use the first calculated box. This helps Speed Index be more stable
and should avoid some asserts we were seeing.

BUG=

Review URL: https://codereview.chromium.org/163023003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252476 0039d316-1c4b-4281-b951-d872f2087c98
Move the kEnablePixelOutputInTests flag to compositor_switches.h

This is so that code in ui/ can make use of the flag. This way
the ui::InitializeContextFactoryForTests() method can decide to
show pixel output or not for each test, as that is where we know
if the test would like pixel output.

TBR=piman@chromium.org
BUG=270918

Review URL: https://codereview.chromium.org/174503003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252477 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252477