Make GMs aware of what tool they're being run in.

Add a saveLayer set of draws to convex_poly_clip and fix GPU bug where polygon clips don't account for the translation between clip and device space.

BUG=skia:2051
R=robertphillips@google.com, reed@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/148283017

git-svn-id: http://skia.googlecode.com/svn/trunk@13371 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/benchmain.cpp b/bench/benchmain.cpp
index 13241e9..ba9bfca 100644
--- a/bench/benchmain.cpp
+++ b/bench/benchmain.cpp
@@ -55,6 +55,7 @@
 
     virtual SkBenchmark* operator()() const SK_OVERRIDE {
         skiagm::GM* gm = fGMFactory(NULL);
+        gm->setMode(skiagm::GM::kBench_Mode);
         return SkNEW_ARGS(SkGMBench, (gm));
     }