Fixed crash in ~VizProcessContextProvider()

Add check for |cache_controller_| in ~VizProcessContextProvider().
It can be nullptr if InitializeContext() failed.

Bug: 1008966
Change-Id: I13204bdf56996850186dcfd312374b05c8161b40
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829546Reviewed-by: Jonathan Ross <jonross@chromium.org>
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700824}

components/viz/service/display_embedder/viz_process_context_provider.cc

@@ -138,7 +138,10 @@ VizProcessContextProvider::~VizProcessContextProvider() {
     base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
         this);
   }
-  cache_controller_->SetGrContext(nullptr);
+
+  // cache_controller_ might ne nullptr if we failed to initialize
+  if (cache_controller_)
+    cache_controller_->SetGrContext(nullptr);
 }
 
 void VizProcessContextProvider::AddRef() const {