Ganesh: images upload to GPU performance fix (skip copying encoded data)

third_party/WebKit/Source/platform/graphics/ThreadSafeDataTransport.cpp

Index: third_party/WebKit/Source/platform/graphics/ThreadSafeDataTransport.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/ThreadSafeDataTransport.cpp b/third_party/WebKit/Source/platform/graphics/ThreadSafeDataTransport.cpp
index e047a0c2ca5846dbee0b0c09f746bd78051ada69..00da86509e5ab2f5879ff49735b19f13191d4c0d 100644
--- a/third_party/WebKit/Source/platform/graphics/ThreadSafeDataTransport.cpp
+++ b/third_party/WebKit/Source/platform/graphics/ThreadSafeDataTransport.cpp
@@ -54,6 +54,14 @@ void ThreadSafeDataTransport::setData(SharedBuffer* buffer, bool allDataReceived
     }
 
     MutexLocker locker(m_mutex);
+    if (m_allDataReceived && newBufferQueue.size()) {

[chrishtr, 2015/12/03 17:51:51]

Is this code reachable in one of your testcases? Not sure why this is necessary.
Apologies if this has already been in the code review thread and I missed it.

[aleksandar.stojiljkovic, 2015/12/03 18:04:14]

No, it is not reachable and it mustn't be. It wasn't checked here before though.
It is necessary as at this point SkData could have been returned and underlying
data shouldn't be changed (appending more data and calling data() could cause
change. Just wanted to prevent future changes in other parts triggering
erroneous situation - hence the ASSERT(false).

[chrishtr, 2015/12/03 18:32:00]

If it is not something that can happen, just put in 
ASSERT(!m_allDataReceived || newBufferQueue.empty());

We should try to avoid adding defensive code.

If the call would be a security/crash bug then RELEASE_ASSERT may be
appropriate.

[aleksandar.stojiljkovic, 2015/12/03 21:17:09]

Done.

+        // This prevents from unexisting use case now - if all data was previously
+        // received, don't append more to it.
+        ASSERT(false);
+        newBufferQueue.clear();
+        return;
+    }
+
     m_newBufferQueue.appendVector(newBufferQueue);
     newBufferQueue.clear();
     m_allDataReceived = allDataReceived;