Add "panel_fitting" GPU feature type and use it for mirror mode.

content/browser/gpu/gpu_blacklist.cc

Index: content/browser/gpu/gpu_blacklist.cc
diff --git a/content/browser/gpu/gpu_blacklist.cc b/content/browser/gpu/gpu_blacklist.cc
index 403a894f92d21ca16c2fdc604ab03335d8acc7b9..0f124c8473fee4c1e7eae4f1e961007aed178d95 100644
--- a/content/browser/gpu/gpu_blacklist.cc
+++ b/content/browser/gpu/gpu_blacklist.cc
@@ -771,6 +771,7 @@ bool GpuBlacklist::GpuBlacklistEntry::SetBlacklistedFeatures(
       case content::GPU_FEATURE_TYPE_FLASH_STAGE3D:
       case content::GPU_FEATURE_TYPE_TEXTURE_SHARING:
       case content::GPU_FEATURE_TYPE_ACCELERATED_VIDEO_DECODE:
+      case content::GPU_FEATURE_TYPE_PANEL_FITTING:
       case content::GPU_FEATURE_TYPE_ALL:
         feature_type |= type;
         break;