webgl: gpu workaround to turn off MSAA

PowerVR.*GX6250 gpu is producing artifacts when
rendering with a context that has antialias set true.

Bug: 1038671, b:148280161
Change-Id: I79081f342bac2531e9d6d43a57939e3c5f8fc0e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2019939Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Fritz Koenig <frkoenig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735217}

content/renderer/webgraphicscontext3d_provider_impl.cc

@@ -110,6 +110,8 @@ WebGraphicsContext3DProviderImpl::GetWebglPreferences() const {
       } else {
         prefs.anti_aliasing_mode = blink::kAntialiasingModeUnspecified;
       }
+    } else if (gpu_feature_info.IsWorkaroundEnabled(WEBGL_MSAA_IS_BROKEN)) {
+      prefs.anti_aliasing_mode = blink::kAntialiasingModeNone;
     }
 
     // Set default context limits for WebGL.

gpu/config/gpu_driver_bug_list.json

@@ -3514,6 +3514,22 @@
       "features": [
         "limit_d3d11_video_decoder_to_11_0"
       ]
+    },
+    {
+      "id": 330,
+      "cr_bugs": [1038671],
+      "description": "WebGL MSAA for PowerVR.*GX6250 context lost with GL_UNKNOWN_CONTEXT_RESET_KHR",
+      "os": {
+        "type": "chromeos"
+      },
+      "gl_vendor": "Imagination.*",
+      "gl_renderer": "PowerVR.*GX6250",
+      "features": [
+        "webgl_msaa_is_broken"
+      ],
+      "disabled_extensions": [
+        "GL_EXT_multisampled_render_to_texture"
+      ]
     }
   ]
 }

gpu/config/gpu_workaround_list.txt

@@ -120,3 +120,4 @@ use_unused_standard_shared_blocks
 use_virtualized_gl_contexts
 validate_multisample_buffer_allocation
 wake_up_gpu_before_drawing
+webgl_msaa_is_broken