Add basic coalescing behavior to the permission bubble manager.

The manager will now wait 400ms after it receives both a request and its view
before showing a bubble.  This allows permissions that are requested
quickly in sequence to be shown together, in only one bubble.  Permission
requests that occur when there is already a bubble visible are queued and not
shown until the current bubble disappears.

This simple wait period is probably simpler than the final design, but is a
good stepping stone toward a better algorithm.

BUG=None

Review URL: https://codereview.chromium.org/150103013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251079 0039d316-1c4b-4281-b951-d872f2087c98
Check for GN args using the union of all rather than individually.

Previously we would check for unused args on a per-build basis. In the GYP build we run the build multiple times, and not all args might be declared in all types of builds. For example, clang args would only be relevant for clang builds, which might only be in the host GYP build.

Makes unused args errors nonfatal. This was coming up a lot in benign cases. It's important to notify people about unused arguments, but it's not critical to block progress on this problem.

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/137713007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251080 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251080