Add can-ignore-rect hint to clear call

src/effects/SkGpuBlurUtils.cpp

Index: src/effects/SkGpuBlurUtils.cpp
===================================================================
--- src/effects/SkGpuBlurUtils.cpp	(revision 12054)
+++ src/effects/SkGpuBlurUtils.cpp	(working copy)
@@ -197,7 +197,7 @@
             // X convolution from reading garbage.
             clearRect = SkIRect::MakeXYWH(srcIRect.fRight, srcIRect.fTop,
                                           radiusX, srcIRect.height());
-            context->clear(&clearRect, 0x0);
+            context->clear(&clearRect, 0x0, false);
         }
         context->setRenderTarget(dstTexture->asRenderTarget());
         SkRect dstRect = SkRect::MakeWH(srcRect.width(), srcRect.height());
@@ -214,7 +214,7 @@
             // convolution from reading garbage.
             clearRect = SkIRect::MakeXYWH(srcIRect.fLeft, srcIRect.fBottom,
                                           srcIRect.width(), radiusY);
-            context->clear(&clearRect, 0x0);
+            context->clear(&clearRect, 0x0, false);
         }
 
         context->setRenderTarget(dstTexture->asRenderTarget());
@@ -231,10 +231,10 @@
         // upsampling.
         clearRect = SkIRect::MakeXYWH(srcIRect.fLeft, srcIRect.fBottom,
                                       srcIRect.width() + 1, 1);
-        context->clear(&clearRect, 0x0);
+        context->clear(&clearRect, 0x0, false);
         clearRect = SkIRect::MakeXYWH(srcIRect.fRight, srcIRect.fTop,
                                       1, srcIRect.height());
-        context->clear(&clearRect, 0x0);
+        context->clear(&clearRect, 0x0, false);
         SkMatrix matrix;
         matrix.setIDiv(srcTexture->width(), srcTexture->height());
         context->setRenderTarget(dstTexture->asRenderTarget());