content: Handle native GpuMemoryBuffer allocation failures properly.

content/browser/gpu/browser_gpu_memory_buffer_manager.cc

Index: content/browser/gpu/browser_gpu_memory_buffer_manager.cc
diff --git a/content/browser/gpu/browser_gpu_memory_buffer_manager.cc b/content/browser/gpu/browser_gpu_memory_buffer_manager.cc
index bd7f053edd5f44d84f96111ae3807822255087eb..2c8ece93eadeca8911aab693bf7b333fdbfe91fb 100644
--- a/content/browser/gpu/browser_gpu_memory_buffer_manager.cc
+++ b/content/browser/gpu/browser_gpu_memory_buffer_manager.cc
@@ -165,7 +165,8 @@ void BrowserGpuMemoryBufferManager::AllocateGpuMemoryBufferForChildProcess(
       new_id, size, format, usage, child_client_id, 0,
       base::Bind(&BrowserGpuMemoryBufferManager::
                      GpuMemoryBufferAllocatedForChildProcess,
-                 weak_ptr_factory_.GetWeakPtr(), child_client_id, callback));
+                 weak_ptr_factory_.GetWeakPtr(), new_id, child_client_id,
+                 callback));
 }
 
 gfx::GpuMemoryBuffer*
@@ -314,6 +315,7 @@ void BrowserGpuMemoryBufferManager::GpuMemoryBufferDeleted(
 }
 
 void BrowserGpuMemoryBufferManager::GpuMemoryBufferAllocatedForChildProcess(
+    gfx::GpuMemoryBufferId id,
     int child_client_id,
     const AllocationCallback& callback,
     const gfx::GpuMemoryBufferHandle& handle) {
@@ -334,19 +336,19 @@ void BrowserGpuMemoryBufferManager::GpuMemoryBufferAllocatedForChildProcess(
 
   BufferMap& buffers = client_it->second;
 
-  BufferMap::iterator buffer_it = buffers.find(handle.id);
+  BufferMap::iterator buffer_it = buffers.find(id);
   DCHECK(buffer_it != buffers.end());
   DCHECK_EQ(buffer_it->second.type, gfx::EMPTY_BUFFER);
 
-  if (handle.is_null()) {
+  // The factory should never return a shared memory backed buffer.

[Avi (use Gerrit), 2015/06/10 17:01:47]

"Should never" implies DCHECK, that it shouldn't happen, and that it's a
programming error if it does. If this is a legitimate error condition that can
happen (as your CL description states) then change this comment.

Rather than "should never", explain the condition for which this can happen and
what it means (e.g. "If the handle isn't valid, that means that the GPU process
crashed or is misbehaving...")

[reveman, 2015/06/10 18:32:09]

Good point. Done.

+  bool valid_handle = !handle.is_null() && handle.id == id &&
+                      handle.type != gfx::SHARED_MEMORY_BUFFER;
+  if (!valid_handle) {
     buffers.erase(buffer_it);
     callback.Run(gfx::GpuMemoryBufferHandle());
     return;
   }
 
-  // The factory should never return a shared memory backed buffer.
-  DCHECK_NE(handle.type, gfx::SHARED_MEMORY_BUFFER);
-
   // Store the type of this buffer so it can be cleaned up if the child
   // process is removed.
   buffer_it->second.type = handle.type;