Force checking of result on all functions in elements.h that return MaybeObject*.

src/elements.h

Index: src/elements.h
===================================================================
--- src/elements.h	(revision 11528)
+++ src/elements.h	(working copy)
@@ -60,18 +60,19 @@
   // can optionally pass in the backing store to use for the check, which must
   // be compatible with the ElementsKind of the ElementsAccessor. If
   // backing_store is NULL, the holder->elements() is used as the backing store.
-  virtual MaybeObject* Get(Object* receiver,
-                           JSObject* holder,
-                           uint32_t key,
-                           FixedArrayBase* backing_store = NULL) = 0;
+  MUST_USE_RESULT virtual MaybeObject* Get(
+      Object* receiver,
+      JSObject* holder,
+      uint32_t key,
+      FixedArrayBase* backing_store = NULL) = 0;
 
   // Modifies the length data property as specified for JSArrays and resizes the
   // underlying backing store accordingly. The method honors the semantics of
   // changing array sizes as defined in EcmaScript 5.1 15.4.5.2, i.e. array that
   // have non-deletable elements can only be shrunk to the size of highest
   // element that is non-deletable.
-  virtual MaybeObject* SetLength(JSArray* holder,
-                                 Object* new_length) = 0;
+  MUST_USE_RESULT virtual MaybeObject* SetLength(JSArray* holder,
+                                                 Object* new_length) = 0;
 
   // Modifies both the length and capacity of a JSArray, resizing the underlying
   // backing store as necessary. This method does NOT honor the semantics of
@@ -79,14 +80,14 @@
   // elements. This method should only be called for array expansion OR by
   // runtime JavaScript code that use InternalArrays and don't care about
   // EcmaScript 5.1 semantics.
-  virtual MaybeObject* SetCapacityAndLength(JSArray* array,
-                                            int capacity,
-                                            int length) = 0;
+  MUST_USE_RESULT virtual MaybeObject* SetCapacityAndLength(JSArray* array,
+                                                            int capacity,
+                                                            int length) = 0;
 
   // Deletes an element in an object, returning a new elements backing store.
-  virtual MaybeObject* Delete(JSObject* holder,
-                              uint32_t key,
-                              JSReceiver::DeleteMode mode) = 0;
+  MUST_USE_RESULT virtual MaybeObject* Delete(JSObject* holder,
+                                              uint32_t key,
+                                              JSReceiver::DeleteMode mode) = 0;
 
   // If kCopyToEnd is specified as the copy_size to CopyElements, it copies all
   // of elements from source after source_start to the destination array.
@@ -101,26 +102,28 @@
   // the source JSObject or JSArray in source_holder. If the holder's backing
   // store is available, it can be passed in source and source_holder is
   // ignored.
-  virtual MaybeObject* CopyElements(JSObject* source_holder,
-                                    uint32_t source_start,
-                                    FixedArrayBase* destination,
-                                    ElementsKind destination_kind,
-                                    uint32_t destination_start,
-                                    int copy_size,
-                                    FixedArrayBase* source = NULL) = 0;
+  MUST_USE_RESULT virtual MaybeObject* CopyElements(
+      JSObject* source_holder,
+      uint32_t source_start,
+      FixedArrayBase* destination,
+      ElementsKind destination_kind,
+      uint32_t destination_start,
+      int copy_size,
+      FixedArrayBase* source = NULL) = 0;
 
-  MaybeObject* CopyElements(JSObject* from_holder,
-                            FixedArrayBase* to,
-                            ElementsKind to_kind,
-                            FixedArrayBase* from = NULL) {
+  MUST_USE_RESULT MaybeObject* CopyElements(JSObject* from_holder,
+                                            FixedArrayBase* to,
+                                            ElementsKind to_kind,
+                                            FixedArrayBase* from = NULL) {
     return CopyElements(from_holder, 0, to, to_kind, 0,
                         kCopyToEndAndInitializeToHole, from);
   }
 
-  virtual MaybeObject* AddElementsToFixedArray(Object* receiver,
-                                               JSObject* holder,
-                                               FixedArray* to,
-                                               FixedArrayBase* from = NULL) = 0;
+  MUST_USE_RESULT virtual MaybeObject* AddElementsToFixedArray(
+      Object* receiver,
+      JSObject* holder,
+      FixedArray* to,
+      FixedArrayBase* from = NULL) = 0;
 
   // Returns a shared ElementsAccessor for the specified ElementsKind.
   static ElementsAccessor* ForKind(ElementsKind elements_kind) {