Fix ExtensionSettingsHandler Back Button crash on Mac.

The permission dialogs on the chrome://extensions are tab modal on Mac, meaning that while the dialog is up the user can navigate Back before closing the dialog. This means the dialog can outlive the ESH, causing a crash when the dialog closes and tries to contact the delegate (the ESH).

BUG=267479
R=yoz@chromium.org

Review URL: https://codereview.chromium.org/24569003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225436 0039d316-1c4b-4281-b951-d872f2087c98
Move Power and Clock observers to Ash

BUG=154856

Review URL: https://codereview.chromium.org/24497002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225437 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225436
cc: Re-enable LayerTreeHostTestStartPageScaleAnimation unit test

Recent changes appear to make the previous flakiness go away.
I can not reproduce it locally any more.

BUG=280508

Review URL: https://codereview.chromium.org/24497003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225438 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225438
Use shlex.split to tokenize command.
This allows to use whitespaces in filenames.

TEST=run:
python tools\bisect-builds.py -a win -c "cmd /c copy /Y ""c:\Program Files (x86)\Google\Chrome\Application\30.0.1599.59\pdf.dll"" %p\\.. && %p %a" -- --enable-print-preview

NOTRY=true

Review URL: https://codereview.chromium.org/24502006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225439 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225439