Allow GMs ato be used as benchmarks. Make convex_poly_clip opt in.

bench/SkGMBench.cpp

Index: bench/SkGMBench.cpp
diff --git a/bench/SkGMBench.cpp b/bench/SkGMBench.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..e1d812476482baeb33c96cdd39421bd39ede7c8a
--- /dev/null
+++ b/bench/SkGMBench.cpp
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkGMBench.h"
+
+SkGMBench::SkGMBench(skiagm::GM* gm) : fGM(gm) {
+    fName.printf("GM:%s", gm->shortName());
+}
+
+SkGMBench::~SkGMBench() { delete fGM; }
+
+const char* SkGMBench::onGetName() {
+    return fName.c_str();
+}
+
+bool SkGMBench::isSuitableFor(Backend backend) {
+    uint32_t flags = fGM->getFlags();
+    switch (backend) {
+        case kGPU_Backend:
+            return !(skiagm::GM::kSkipGPU_Flag & flags);
+        case kPDF_Backend:
+            return !(skiagm::GM::kSkipPDF_Flag & flags);
+        case kRaster_Backend:
+            // GM doesn't have an equivalent flag. If the GM has known issues with 565 then
+            // we skip it for ALL raster configs in bench.
+            return !(skiagm::GM::kSkip565_Flag & flags);
+        case kNonRendering_Backend:
+            return false;
+        default:
+            SkDEBUGFAIL("Unexpected backend type.");
+            return false;
+    }
+}
+
+void SkGMBench::onDraw(const int loops, SkCanvas* canvas) {
+    // Do we care about timing the draw of the background (once)?
+    // Does the GM ever rely on drawBackground to lazily compute something?
+    fGM->drawBackground(canvas);
+    for (int i = 0; i < loops; ++i) {
+        fGM->drawContent(canvas);
+    }
+}
+
+SkIPoint SkGMBench::onGetSize() {
+    SkISize size = fGM->getISize();
+    return SkIPoint::Make(size.fWidth, size.fHeight);
+}