linux: implement gpu plugin

chrome/renderer/command_buffer_proxy.cc

Index: chrome/renderer/command_buffer_proxy.cc
diff --git a/chrome/renderer/command_buffer_proxy.cc b/chrome/renderer/command_buffer_proxy.cc
index b78fa84e83bfaff3ff276e9f03d87367ce7f23b5..3b68cc216dd7ffcc16aa6c30f2ed7ae41ac996ef 100644
--- a/chrome/renderer/command_buffer_proxy.cc
+++ b/chrome/renderer/command_buffer_proxy.cc
@@ -153,12 +153,20 @@ Buffer CommandBufferProxy::GetTransferBuffer(int32 id) {
   }
 
   // Cache the transfer buffer shared memory object client side.
+#if defined(OS_WIN)
+  // TODO(piman): Does Windows needs this version of the constructor ? It
+  // duplicates the handle, but I'm not sure why it is necessary - it was
+  // already duped by the CommandBufferStub.
   base::SharedMemory* shared_memory =
       new base::SharedMemory(handle, false, base::GetCurrentProcessHandle());
+#else
+  base::SharedMemory* shared_memory =
+      new base::SharedMemory(handle, false);
+#endif
 
   // Map the shared memory on demand.
   if (!shared_memory->memory()) {
-    if (!shared_memory->Map(shared_memory->max_size())) {
+    if (!shared_memory->Map(size)) {
       delete shared_memory;
       return Buffer();
     }