Mac: Disable CATransactionGPUCoordinator to test crash theory

Crashes with content::GpuProcessHost::OnProcessCrashed on the stack
have become prevalent in Chrome 69.

CATransactionGPUCoordinator was introduced in the first Canary to
exhibit these crashes (https://crrev.com/565687 in 69.0.3455.0).

Disable CATransactionGPUCoordinator to test the theory that it is
responsible for the crashes. This will make window resize slightly
jankier (like -- the window's contents will detach from the window
during resize) while disabled. Note that not all window resize logic
is disabled by this -- just the GPU side (so resize will be reasonable
most of the time, but there will be occaisonal glitches now).

Bug: 871430
Change-Id: Ifec51e511712b9843f15e9b8c43b66d852232b89
Reviewed-on: https://chromium-review.googlesource.com/1164555Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581117}

content/browser/gpu/gpu_process_host.cc

@@ -703,8 +703,9 @@ GpuProcessHost::GpuProcessHost(int host_id, GpuProcessKind kind)
       process_launched_(false),
       status_(UNKNOWN),
 #if defined(OS_MACOSX)
-      ca_transaction_gpu_coordinator_(
-          base::MakeRefCounted<CATransactionGPUCoordinator>(this)),
+      // TODO(ccameron): This is temporarily disabled to see if it is the cause
+      // of https://crbug.com/871430
+      ca_transaction_gpu_coordinator_(nullptr),
 #endif
       gpu_host_binding_(this),
       weak_ptr_factory_(this) {
@@ -733,8 +734,10 @@ GpuProcessHost::~GpuProcessHost() {
   SendOutstandingReplies(EstablishChannelStatus::GPU_HOST_INVALID);
 
 #if defined(OS_MACOSX)
-  ca_transaction_gpu_coordinator_->HostWillBeDestroyed();
-  ca_transaction_gpu_coordinator_ = nullptr;
+  if (ca_transaction_gpu_coordinator_) {
+    ca_transaction_gpu_coordinator_->HostWillBeDestroyed();
+    ca_transaction_gpu_coordinator_ = nullptr;
+  }
 #endif
 
   if (status_ == UNKNOWN) {