Move some work from backend onClear to base class clear

src/gpu/GrGpu.cpp

Index: src/gpu/GrGpu.cpp
diff --git a/src/gpu/GrGpu.cpp b/src/gpu/GrGpu.cpp
index bb020f5b503d7ac7c7207fcc663e37e00542bab2..24cd08a1b60f9a5848d08ba9d5b9ed0be1317134 100644
--- a/src/gpu/GrGpu.cpp
+++ b/src/gpu/GrGpu.cpp
@@ -222,7 +222,24 @@ void GrGpu::clear(const SkIRect* rect,
                   GrRenderTarget* renderTarget) {
     SkASSERT(renderTarget);
     this->handleDirtyContext();
-    this->onClear(renderTarget, rect, color, canIgnoreRect);
+
+    if (canIgnoreRect && this->caps()->fullClearIsFree()) {
+        rect = NULL;
+    }
+
+    SkIRect clippedRect;
+    if (rect) {
+        // flushScissor expects rect to be clipped to the target.
+        clippedRect = *rect;
+        SkIRect rtRect = SkIRect::MakeWH(renderTarget->width(), renderTarget->height());
+        if (clippedRect.intersect(rtRect)) {

[egdaniel, 2015/08/05 19:59:05]

I wonder if its worth also checking if the clippedRect ends being equal to
rtRect and setting rect to NULL so it simply does a full clear.

[bsalomon, 2015/08/05 20:18:57]

Should this all be done even higher up (e.g. GrDT)?

+            rect = &clippedRect;
+        } else {
+            return;
+        }
+    }
+
+    this->onClear(renderTarget, rect, color);
 }
 
 void GrGpu::clearStencilClip(const SkIRect& rect,