Update V8 to r7427: Initial merge by git

As required by WebKit r82507

Change-Id: I7ae83ef3f689356043b4929255b7c1dd31d8c5df
diff --git a/src/codegen.h b/src/codegen.h
index 23b36f0..aa31999 100644
--- a/src/codegen.h
+++ b/src/codegen.h
@@ -92,26 +92,26 @@
 // of active code generators.
 class CodeGeneratorScope BASE_EMBEDDED {
  public:
-  explicit CodeGeneratorScope(CodeGenerator* cgen) {
-    previous_ = top_;
-    top_ = cgen;
+  explicit CodeGeneratorScope(Isolate* isolate, CodeGenerator* cgen)
+      : isolate_(isolate) {
+    previous_ = isolate->current_code_generator();
+    isolate->set_current_code_generator(cgen);
   }
 
   ~CodeGeneratorScope() {
-    top_ = previous_;
+    isolate_->set_current_code_generator(previous_);
   }
 
-  static CodeGenerator* Current() {
-    ASSERT(top_ != NULL);
-    return top_;
+  static CodeGenerator* Current(Isolate* isolate) {
+    ASSERT(isolate->current_code_generator() != NULL);
+    return isolate->current_code_generator();
   }
 
  private:
-  static CodeGenerator* top_;
   CodeGenerator* previous_;
+  Isolate* isolate_;
 };
 
-
 #if V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_X64
 
 // State of used registers in a virtual frame.