Major bench refactoring.
   - Use FLAGS_.
   - Remove outer repeat loop.
   - Tune inner loop automatically.

BUG=skia:1590
R=epoger@google.com, scroggo@google.com

Review URL: https://codereview.chromium.org/23478013

git-svn-id: http://skia.googlecode.com/svn/trunk@11187 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/XfermodeBench.cpp b/bench/XfermodeBench.cpp
index 0f70a4c..993fc8f 100644
--- a/bench/XfermodeBench.cpp
+++ b/bench/XfermodeBench.cpp
@@ -36,7 +36,7 @@
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         SkISize size = canvas->getDeviceSize();
         SkRandom random;
-        for (int i = 0; i < kNumRects; ++i) {
+        for (int i = 0; i < this->getLoops(); ++i) {
             SkPaint paint;
             paint.setXfermode(fXfermode.get());
             paint.setColor(random.nextU());
@@ -54,7 +54,6 @@
 
 private:
     enum {
-        kNumRects = SkBENCHLOOP(75),
         kMinSize = 50,
         kMaxSize = 100,
     };