Eliminate copies of encoded image data

third_party/WebKit/Source/web/WebImageDecoder.cpp

Index: third_party/WebKit/Source/web/WebImageDecoder.cpp
diff --git a/third_party/WebKit/Source/web/WebImageDecoder.cpp b/third_party/WebKit/Source/web/WebImageDecoder.cpp
index 2961bd8c6274d9c45279936f8e49bdc3c7d41a79..5d3728522e5ab381b2244c9e5d07b2ecc61920c1 100644
--- a/third_party/WebKit/Source/web/WebImageDecoder.cpp
+++ b/third_party/WebKit/Source/web/WebImageDecoder.cpp
@@ -31,6 +31,7 @@
 #include "public/web/WebImageDecoder.h"
 
 #include "platform/SharedBuffer.h"
+#include "platform/image-decoders/SharedBufferSegmentReader.h"
 #include "platform/image-decoders/bmp/BMPImageDecoder.h"
 #include "platform/image-decoders/ico/ICOImageDecoder.h"
 #include "public/platform/Platform.h"
@@ -65,7 +66,9 @@ void WebImageDecoder::init(Type type)
 void WebImageDecoder::setData(const WebData& data, bool allDataReceived)
 {
     ASSERT(m_private);
-    m_private->setData(PassRefPtr<SharedBuffer>(data).get(), allDataReceived);
+    RefPtr<SharedBuffer> buffer = PassRefPtr<SharedBuffer>(data).get();

[Peter Kasting, 2016/03/23 02:42:59]

Nit: Can't we just do something like RefPtr<SharedBuffer> buffer(data); ?

[scroggo_chromium, 2016/03/24 13:59:46]

I don't think so. WebData has a "operator PassRefPtr<SharedBuffer>() const" that
allows this conversion. I tried exactly what you proposed, and it did not work,
but I cannot promise that there is not some other incantation that will.

[Peter Kasting, 2016/03/24 22:05:43]

Yeah, I had been hoping the compiler could figure out that there was a RefPtr
constructor taking a PassRefPtr, and then implicitly invoke that operator.  But
if we have to be explicit about it, so be it.

+    RefPtr<SharedBufferSegmentReader> segmentReader = adoptRef(new SharedBufferSegmentReader(buffer.get()));
+    m_private->setData(segmentReader.get(), allDataReceived);
 }
 
 bool WebImageDecoder::isFailed() const