Initial checkin of the compositor_model_bench tool

This tool simulates the GPU demands of Chromium's GPU-accelerated compositor. In
the current version, we simulate the performance of the existing forward
rendering model; coming changes will prototype a new model.

BUG=None
TEST=self

This is http://codereview.chromium.org/7718020/ with trivial fixes
Original change by Joshua Trask <joshtrask@google.com>

Review URL: http://codereview.chromium.org/7792002
Patch from Joshua Trask <joshtrask@google.com>.

git-svn-id: http://src.chromium.org/svn/trunk/src/build@98706 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

all.gyp

@@ -18,6 +18,7 @@
         '../ui/ui.gyp:*',
         '../gpu/gpu.gyp:*',
         '../gpu/demos/demos.gyp:*',
+        '../gpu/tools/tools.gyp:*',
         '../ipc/ipc.gyp:*',
         '../jingle/jingle.gyp:*',
         '../media/media.gyp:*',