Add a switch to TestRunner to enable/disable mock spell checker

components/test_runner/spell_check_client.h

Index: components/test_runner/spell_check_client.h
diff --git a/components/test_runner/spell_check_client.h b/components/test_runner/spell_check_client.h
index f9f23cb1191e1dabcbd4e5e71bd254bd997df65b..c7bb376d3dbd99e172d0a0235fea24812f9a3048 100644
--- a/components/test_runner/spell_check_client.h
+++ b/components/test_runner/spell_check_client.h
@@ -30,6 +30,7 @@ class SpellCheckClient : public blink::WebSpellCheckClient {
   virtual ~SpellCheckClient();
 
   void SetDelegate(WebTestDelegate* delegate);
+  void SetEnabled(bool enabled);
 
   // blink::WebSpellCheckClient implementation.
   void spellCheck(
@@ -47,6 +48,10 @@ class SpellCheckClient : public blink::WebSpellCheckClient {
  private:
   void FinishLastTextCheck();
 
+  // Do not perform any checking when |enabled_ == false|.
+  // Tests related to spell checking should enable it manually.
+  bool enabled_ = false;
+
   // The mock spellchecker used in spellCheck().
   MockSpellCheck spell_check_;