Use approximate scratch textures for image filters.

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 07b7f75e92a2bd2ff9a269855fe526fe39de6287..096b848ab0c2e02babd5d4f7a1f68f0004ba224f 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -1763,11 +1763,13 @@ SkBaseDevice* SkGpuDevice::onCreateDevice(const SkImageInfo& info, Usage usage)
     unsigned flags = info.isOpaque() ? 0 : kNeedClear_Flag;
 
 #if CACHE_COMPATIBLE_DEVICE_TEXTURES
-    // layers are never draw in repeat modes, so we can request an approx
-    // match and ignore any padding.
-    const GrContext::ScratchTexMatch match = (kSaveLayer_Usage == usage) ?
-                                                GrContext::kApprox_ScratchTexMatch :
-                                                GrContext::kExact_ScratchTexMatch;
+    // layers are never draw in repeat modes or with mip maps, so we can request an approx
+    // match and ignore any padding. Image filters (at present) don't tile their inputs or use mip
+    // maps, either.
+    const GrContext::ScratchTexMatch match =
+        (kSaveLayer_Usage == usage || kImageFilter_Usage == usage) ?
+            GrContext::kApprox_ScratchTexMatch :
+            GrContext::kExact_ScratchTexMatch;
     texture.reset(fContext->refScratchTexture(desc, match));
 #else
     texture.reset(fContext->createUncachedTexture(desc, NULL, 0));