Early terminate GetBucketContents if WaitForCmd fails

This should avoid the scenario outlined in crbug.com/1371859 where the
command isn't run due to the GPU process shutting down, but the memcpy
is attempted anyway.

Bug: 1371859
Change-Id: Ib2a4b735365f29d092be8003ba668854be1d5c3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4076865
Reviewed-by: Victor Miura <vmiura@chromium.org>
Commit-Queue: Brandon Jones <bajones@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1078779}

gpu/command_buffer/client/implementation_base.cc

@@ -256,9 +256,9 @@ gpu::ContextResult ImplementationBase::Initialize(
   return gpu::ContextResult::kSuccess;
 }
 
-void ImplementationBase::WaitForCmd() {
+bool ImplementationBase::WaitForCmd() {
   TRACE_EVENT0("gpu", "ImplementationBase::WaitForCmd");
-  helper_->Finish();
+  return helper_->Finish();
 }
 
 int32_t ImplementationBase::GetResultShmId() {
@@ -301,7 +301,9 @@ bool ImplementationBase::GetBucketContents(uint32_t bucket_id,
         }
         helper_->GetBucketData(bucket_id, offset, buffer.size(),
                                buffer.shm_id(), buffer.offset());
-        WaitForCmd();
+        if (!WaitForCmd()) {
+          return false;
+        }
       }
       uint32_t size_to_copy = std::min(size, buffer.size());
       memcpy(&(*data)[offset], buffer.address(), size_to_copy);

gpu/command_buffer/client/implementation_base.h

@@ -105,7 +105,7 @@ class GLES2_IMPL_EXPORT ImplementationBase
   gpu::ContextResult Initialize(const SharedMemoryLimits& limits);
 
   // Waits for all commands to execute.
-  void WaitForCmd();
+  bool WaitForCmd();
 
   // Gets the value of the result.
   template <typename T>