Revert "Look for why ChromeOS bots are flakily using software compositing."

This reverts commit 1050c3ac.

Reason for revert: Did it's job.

Original change's description:
> Look for why ChromeOS bots are flakily using software compositing.
> 
> This adds some NOTREACHED() on ChromeOS to figure out why tests are
> disabling gpu compositing.
> 
> R=​zmo@chromium.org
> 
> Bug: 793303
> Change-Id: I6ee99fc334c34c292bcb1e3568108e422d43da4c
> Reviewed-on: https://chromium-review.googlesource.com/826382
> Reviewed-by: Zhenyao Mo <zmo@chromium.org>
> Commit-Queue: danakj <danakj@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#523958}

TBR=danakj@chromium.org,zmo@chromium.org

Change-Id: I439a4775e1dfa9329da9cbbd416a4bad11bd71e6
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 793303
Reviewed-on: https://chromium-review.googlesource.com/827142Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524081}

content/browser/compositor/gpu_process_transport_factory.cc

@@ -355,21 +355,11 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
       gpu_channel_host->gpu_feature_info()
               .status_values[gpu::GPU_FEATURE_TYPE_GPU_COMPOSITING] !=
           gpu::kGpuFeatureStatusEnabled) {
-#if defined(OS_CHROMEOS)
-    // TODO(crbug.com/793303): We shouldn't blacklist gpu compositing on
-    // ChromeOS.
-    NOTREACHED();
-#endif
     use_gpu_compositing = false;
   }
   // Gpu compositing may have been disabled in the meantime.
-  if (is_gpu_compositing_disabled_) {
-#if defined(OS_CHROMEOS)
-    // TODO(crbug.com/793303): We shouldn't have gpu disabled on ChromeOS.
-    NOTREACHED();
-#endif
+  if (is_gpu_compositing_disabled_)
     use_gpu_compositing = false;
-  }
 
   // The widget might have been released in the meantime.
   PerCompositorDataMap::iterator it =
@@ -403,11 +393,6 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
     // If not using GL compositing, don't keep the old shared worker context.
     shared_worker_context_provider_ = nullptr;
   } else if (!gpu_channel_host) {
-#if defined(OS_CHROMEOS)
-    // TODO(crbug.com/793303): We shouldn't fail to make a GpuChannelHost on
-    // ChromeOS.
-    NOTREACHED();
-#endif
     // Failed to establish a channel, which is a fatal error, so stop trying to
     // use gpu compositing.
     use_gpu_compositing = false;
@@ -440,14 +425,8 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
       auto result = shared_worker_context_provider_->BindToCurrentThread();
       if (result != gpu::ContextResult::kSuccess) {
         shared_worker_context_provider_ = nullptr;
-        if (result == gpu::ContextResult::kFatalFailure) {
-#if defined(OS_CHROMEOS)
-          // TODO(crbug.com/793303): We shouldn't have fatal context failures on
-          // ChromeOS.
-          NOTREACHED();
-#endif
+        if (result == gpu::ContextResult::kFatalFailure)
           use_gpu_compositing = false;
-        }
       }
     }
 
@@ -475,14 +454,8 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
       auto result = context_provider->BindToCurrentThread();
       if (result != gpu::ContextResult::kSuccess) {
         context_provider = nullptr;
-        if (result == gpu::ContextResult::kFatalFailure) {
-#if defined(OS_CHROMEOS)
-          // TODO(crbug.com/793303): We shouldn't have fatal context failures on
-          // ChromeOS.
-          NOTREACHED();
-#endif
+        if (result == gpu::ContextResult::kFatalFailure)
           use_gpu_compositing = false;
-        }
       }
     }
   }