Remove superfluous ThreadLocalTop::catcher field.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index ab62d371dce328088b0238970aa1a5e7c5f813cb..e8c2a711ed81ccf9fe8d80abc484179f4e6b3fe4 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -292,7 +292,6 @@ class ThreadLocalTop BASE_EMBEDDED {
   Object* scheduled_exception_;
   bool external_caught_exception_;
   SaveContext* save_context_;
-  v8::TryCatch* catcher_;
 
   // Stack.
   Address c_entry_fp_;  // the frame pointer of the top c entry frame
@@ -618,8 +617,6 @@ class Isolate {
     return &thread_local_top_.external_caught_exception_;
   }
 
-  THREAD_LOCAL_TOP_ACCESSOR(v8::TryCatch*, catcher)
-
   THREAD_LOCAL_TOP_ADDRESS(Object*, scheduled_exception)
 
   Address pending_message_obj_address() {
@@ -644,7 +641,6 @@ class Isolate {
     thread_local_top_.scheduled_exception_ = heap_.the_hole_value();
   }
 
-  bool HasExternalTryCatch();
   bool IsFinallyOnTop();
 
   bool is_catchable_by_javascript(Object* exception) {
@@ -708,23 +704,19 @@ class Isolate {
 
   class ExceptionScope {
    public:
-    explicit ExceptionScope(Isolate* isolate) :
-      // Scope currently can only be used for regular exceptions,
-      // not termination exception.
-      isolate_(isolate),
-      pending_exception_(isolate_->pending_exception(), isolate_),
-      catcher_(isolate_->catcher())
-    { }
+    // Scope currently can only be used for regular exceptions,
+    // not termination exception.
+    explicit ExceptionScope(Isolate* isolate)
+        : isolate_(isolate),
+          pending_exception_(isolate_->pending_exception(), isolate_) {}
 
     ~ExceptionScope() {
-      isolate_->set_catcher(catcher_);
       isolate_->set_pending_exception(*pending_exception_);
     }
 
    private:
     Isolate* isolate_;
     Handle<Object> pending_exception_;
-    v8::TryCatch* catcher_;
   };
 
   void SetCaptureStackTraceForUncaughtExceptions(