Make so that array length property access uses a new IC that tracks the array map.

src/arm/stub-cache-arm.cc

Index: src/arm/stub-cache-arm.cc
diff --git a/src/arm/stub-cache-arm.cc b/src/arm/stub-cache-arm.cc
index d3b58624c8b24058eda3cdec1742bc7ccc36c739..392b562dd36136cdeed5b7e1f70380ff6780dd49 100644
--- a/src/arm/stub-cache-arm.cc
+++ b/src/arm/stub-cache-arm.cc
@@ -2955,6 +2955,56 @@ Handle<Code> LoadStubCompiler::CompileLoadCallback(
 #define __ ACCESS_MASM(masm)
 
 
+void LoadStubCompiler::GenerateLoadArrayLength(
+    MacroAssembler* masm,
+    Register holder) {
+  // ----------- S t a t e -------------
+  //  -- r0    : receiver
+  //  -- r2    : name
+  //  -- lr    : return address
+  // -----------------------------------
+
+  // Load length directly from the JS array.
+  __ ldr(r0, FieldMemOperand(holder, JSArray::kLengthOffset));
+  __ Ret();
+}
+
+
+#undef __
+#define __ ACCESS_MASM(masm())
+
+
+Handle<Code> LoadStubCompiler::CompileLoadArrayLength(
+    Handle<String> name,
+    Handle<JSObject> receiver,
+    Handle<JSObject> holder) {
+  // ----------- S t a t e -------------
+  //  -- r0    : receiver
+  //  -- r2    : name
+  //  -- lr    : return address
+  // -----------------------------------
+  Label miss;
+
+  // Check that the maps haven't changed.
+  __ JumpIfSmi(r0, &miss);
+  Register holder_reg = CheckPrototypes(
+      receiver, r0, holder, r3, r4, r1, name, &miss);
+
+  GenerateLoadArrayLength(masm(), holder_reg);
+
+  __ bind(&miss);
+  GenerateLoadMiss(masm(), Code::LOAD_IC);
+
+  // Return the generated code.
+  return GetCode(Code::CALLBACKS, name,
+                 Code::ExtraICStateForeignCallbackArrayLength);
+}
+
+
+#undef __
+#define __ ACCESS_MASM(masm)
+
+
 void LoadStubCompiler::GenerateLoadViaGetter(MacroAssembler* masm,
                                              Handle<JSFunction> getter) {
   // ----------- S t a t e -------------