[GCM] Make sure GCM checkout logic is invoked when the profile is signed out

We now always create GCMProfileService that listens to profile
notifications such that GCM checkout logic could be invoked when the
profile is signed out.

We now move the GCM check-in logic from GCMClient::Initialize to GCMClient::CheckIn.

BUG=344031
TEST=new tests added and existing tests updated

Review URL: https://codereview.chromium.org/165993005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253787 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253787
Make BeginRequest code more readable

- move declarations of variables to the place where they're actually
  used
- remove unnecessary alias to new_request

BUG=none

Review URL: https://codereview.chromium.org/180913002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253788 0039d316-1c4b-4281-b951-d872f2087c98
Add support for safe math operations in base/numerics

Add checked numeric templates.

BUG=332611

Review URL: https://codereview.chromium.org/141583008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253789 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253789