Initial implementation of GetStackSample sampling profiler API.

src/vm-state.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_VM_STATE_H_
 #define V8_VM_STATE_H_
 
 #include "src/allocation.h"
 #include "src/isolate.h"
 
 namespace v8 {
 namespace internal {
 
+// Logging and profiling.  A StateTag represents a possible state of
+// the VM. The logger maintains a stack of these. Creating a VMState
+// object enters a state by pushing on the stack, and destroying a
+// VMState object leaves a state by popping the current state from the
+// stack.
 template <StateTag Tag>
 class VMState BASE_EMBEDDED {
  public:
   explicit inline VMState(Isolate* isolate);
   inline ~VMState();
 
  private:
   Isolate* isolate_;
   StateTag previous_tag_;
 };
@@ skipping 14 matching lines @@
   ExternalCallbackScope* previous_scope_;
 #ifdef USE_SIMULATOR
   Address scope_address_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_VM_STATE_H_