GitLab

Introduce NewTabButtonTargeter, a derived class of 
MaskedViewTargeter, to define the custom hit-test 
region of the new tab button.

BUG=377551
TEST=none

Review URL: https://codereview.chromium.org/299353007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274041 0039d316-1c4b-4281-b951-d872f2087c98