Remove ContextProvider::IsContextLost.

cc/output/context_provider.h

Index: cc/output/context_provider.h
diff --git a/cc/output/context_provider.h b/cc/output/context_provider.h
index dfaab4a15b214d6e55d4b7a7e3b743f193be3801..aa4367d97ff68d515b22121b7cb89b25fba4ad57 100644
--- a/cc/output/context_provider.h
+++ b/cc/output/context_provider.h
@@ -58,9 +58,6 @@ class ContextProvider : public base::RefCountedThreadSafe<ContextProvider> {
   // Returns the capabilities of the currently bound 3d context.
   virtual Capabilities ContextCapabilities() = 0;
 
-  // Checks if the context is currently known to be lost.
-  virtual bool IsContextLost() = 0;
-
   // Ask the provider to check if the contexts are valid or lost. If they are,
   // this should invalidate the provider so that it can be replaced with a new
   // one.