cc: Changed picture clones to emit an alias trace.

cc: Changed picture clones to emit an alias trace.

This patch changes the tracing snapshot code for pictures to emit a
much smaller message for picture clones. The regular picture message
looks like the following:

{
  params: {
   layer_rect: { ... },
   opaque_rect: { ... },
  },
  skp64: { /* large chunk here */ }
}

That message is generated for both the original picture and its clones.

The format for the original picture stays the same, but the clone
message becomes the following:

{
  alias: { id_ref: { /* id of the original */ } }
}

This change has to be accompanied by a small change to trace-viewer
to handle the new message correctly.

Note this also includes a trace-viewer DEPS roll.

R=nduca@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23717012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221102 0039d316-1c4b-4281-b951-d872f2087c98