Reapply r9673 "Scope tree serialization and ScopeIterator cleanup."

Reapply r9673 "Scope tree serialization and ScopeIterator cleanup."

This also includes the two fixes from r9674 and r9675. Here's the diff
to the previous CL.

 --- a/src/runtime.cc
 +++ b/src/runtime.cc
 @@ -11133,17 +11133,26 @@ class ScopeIterator {
        context_(Context::cast(frame->context())),
        nested_scope_chain_(4) {

 +    // Catch the case when the debugger stops in an internal function.
 +    Handle<SharedFunctionInfo> shared_info(function_->shared());
 +    if (shared_info->script() == isolate->heap()->undefined_value()) {
 +      if (shared_info->scope_info()->HasContext()) Next();
 +      return;
 +    }
 +
      // Check whether we are in global code or function code. If there is a stack
      // slot for .result then this function has been created for evaluating
      // global code and it is not a real function.
      // Checking for the existence of .result seems fragile, but the scope info
      // saved with the code object does not otherwise have that information.
 -    int index = function_->shared()->scope_info()->
 +    int index = shared_info->scope_info()->
          StackSlotIndex(isolate_->heap()->result_symbol());

      // Reparse the code and analyze the scopes.
      ZoneScope zone_scope(isolate, DELETE_ON_EXIT);
 -    Handle<SharedFunctionInfo> shared_info(function_->shared());
      Handle<Script> script(Script::cast(shared_info->script()));
      Scope* scope;
      if (index >= 0) {

Committed: http://code.google.com/p/v8/source/detail?r=9734

[Steven, 2011-10-19 15:56:55]

PTAL. Will also run WebKit tests over night.

[Steven, 2011-10-20 08:11:54]

Did a small change in skipping (nested) contexts in an internal function.

[Kevin Millikin (Chromium), 2011-10-21 10:15:44]

This LGTM.