add readPixels to SkSurface (later try to remove it from SkCanvas)

src/image/SkSurface.cpp

Index: src/image/SkSurface.cpp
diff --git a/src/image/SkSurface.cpp b/src/image/SkSurface.cpp
index 3ca5747252bd147da14c18ec8f5494bca99291c7..13b7d65546172c604f0ff257838fde8062470e37 100644
--- a/src/image/SkSurface.cpp
+++ b/src/image/SkSurface.cpp
@@ -170,6 +170,20 @@ const void* SkSurface::peekPixels(SkImageInfo* info, size_t* rowBytes) {
     return this->getCanvas()->peekPixels(info, rowBytes);
 }
 
+bool SkSurface::readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                           int srcX, int srcY) {
+    return this->getCanvas()->readPixels(dstInfo, dstPixels, dstRowBytes, srcX, srcY);
+}
+
+bool SkSurface::readPixels(SkBitmap* dst, const SkIRect* srcRect) {
+    SkIRect storage;
+    if (NULL == srcRect) {
+        storage.set(0, 0, this->width(), this->height());
+        srcRect = &storage;
+    }
+    return this->getCanvas()->readPixels(*srcRect, dst);
+}
+
 //////////////////////////////////////////////////////////////////////////////////////
 #ifdef SK_SUPPORT_LEGACY_TEXTRENDERMODE