cc: Avoid ResourceProvider nullptr deref

cc/trees/layer_tree_host_unittest_context.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/memory/ptr_util.h"
 #include "cc/layers/heads_up_display_layer.h"
 #include "cc/layers/layer_impl.h"
@@ skipping 1427 matching lines @@
       case 3:
         LoseContext();
         break;
     }
   }
 
   void DidActivateTreeOnThread(LayerTreeHostImpl* impl) override {
     LayerTreeHostContextTest::DidActivateTreeOnThread(impl);
     switch (time_step_) {
       case 1:
-        // The pending requests on the impl-side should have been processed.
-        EXPECT_NE(0u, impl->ResourceIdForUIResource(ui_resource_->id()));
+        // The pending requests on the impl-side should not have been processed
+        // since the context was lost. But we should have marked the resource as
+        // evicted instead.
+        EXPECT_EQ(0u, impl->ResourceIdForUIResource(ui_resource_->id()));
+        EXPECT_TRUE(impl->EvictedUIResourcesExist());
         break;
       case 2:
-        // The "lost resource" callback should have been called once.
+        // The "lost resource" callback should have been called once and it
+        // should have gotten recreated now and shouldn't be marked as evicted
+        // anymore.
         EXPECT_EQ(1, ui_resource_->lost_resource_count);
+        EXPECT_NE(0u, impl->ResourceIdForUIResource(ui_resource_->id()));
+        EXPECT_FALSE(impl->EvictedUIResourcesExist());
         break;
       case 4:
         // The resource is deleted and should not be in the manager.  Use
         // test_id_ since ui_resource_ has been deleted.
         EXPECT_EQ(0u, impl->ResourceIdForUIResource(test_id_));
         break;
     }
 
     PostStepCompleteToMainThread();
     ++time_step_;
@@ skipping 165 matching lines @@
 
   bool deferred_ = false;
   bool lost_ = true;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(
     LayerTreeHostContextTestLoseAfterSendingBeginMainFrame);
 
 }  // namespace
 }  // namespace cc