Handle all context lost reasons when determining guilt of domain.

This avoids a NOTREACHED() in the previous code. Verified that addition
of new constants without updating the switch statement will cause a
compile failure.

BUG=615113
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel;tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2029293002
Cr-Commit-Position: refs/heads/master@{#397906}

content/browser/gpu/gpu_process_host.cc

@@ -879,19 +879,25 @@ void GpuProcessHost::OnDidLoseContext(bool offscreen,
     return;
   }
 
-  GpuDataManagerImpl::DomainGuilt guilt;
+  GpuDataManagerImpl::DomainGuilt guilt =
+      GpuDataManagerImpl::DOMAIN_GUILT_UNKNOWN;
   switch (reason) {
     case gpu::error::kGuilty:
       guilt = GpuDataManagerImpl::DOMAIN_GUILT_KNOWN;
       break;
+    // Treat most other error codes as though they had unknown provenance.
+    // In practice this doesn't affect the user experience. A lost context
+    // of either known or unknown guilt still causes user-level 3D APIs
+    // (e.g. WebGL) to be blocked on that domain until the user manually
+    // reenables them.
     case gpu::error::kUnknown:
-      guilt = GpuDataManagerImpl::DOMAIN_GUILT_UNKNOWN;
+    case gpu::error::kOutOfMemory:
+    case gpu::error::kMakeCurrentFailed:
+    case gpu::error::kGpuChannelLost:
+    case gpu::error::kInvalidGpuMessage:
       break;
     case gpu::error::kInnocent:
       return;
-    default:
-      NOTREACHED();
-      return;
   }
 
   GpuDataManagerImpl::GetInstance()->BlockDomainFrom3DAPIs(url, guilt);

gpu/command_buffer/common/constants.h

@@ -57,7 +57,7 @@ namespace error {
     // client-side.
     kInvalidGpuMessage,
 
-    kContextLostReasonLast = kGpuChannelLost
+    kContextLostReasonLast = kInvalidGpuMessage
   };
 }