Optimize SkTileImageFilter in an offset filter when possible.

src/effects/SkTileImageFilter.cpp

Index: src/effects/SkTileImageFilter.cpp
diff --git a/src/effects/SkTileImageFilter.cpp b/src/effects/SkTileImageFilter.cpp
index ca4c15d4191900fc644cdb3961096bcb8b4bf125..5d74295fd8373057aa44b51d608b1c7accac6c99 100644
--- a/src/effects/SkTileImageFilter.cpp
+++ b/src/effects/SkTileImageFilter.cpp
@@ -9,6 +9,7 @@
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkDevice.h"
+#include "SkOffsetImageFilter.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 #include "SkMatrix.h"
@@ -21,6 +22,17 @@ SkImageFilter* SkTileImageFilter::Create(const SkRect& srcRect, const SkRect& ds
     if (!SkIsValidRect(srcRect) || !SkIsValidRect(dstRect)) {
         return nullptr;
     }

[robertphillips, 2016/01/12 14:18:29]

Can this fit on one line ?

[Stephen White, 2016/01/12 14:23:12]

Done.

+    if (srcRect.width() == dstRect.width() &&
+        srcRect.height() == dstRect.height()) {
+        SkRect ir = dstRect;
+        if (!ir.intersect(srcRect)) {
+            return SkSafeRef(input);
+        }
+        CropRect cropRect(ir);
+        return SkOffsetImageFilter::Create(dstRect.x() - srcRect.x(),
+                                           dstRect.y() - srcRect.y(),
+                                           input, &cropRect);
+    }
     return new SkTileImageFilter(srcRect, dstRect, input);
 }