Only double align in PagedSpace::AllocateRawDoubleAligned when allocation succeeded.

BUG=chromium:486003
LOG=n

Review URL: https://codereview.chromium.org/1136783002

Cr-Commit-Position: refs/heads/master@{#28326}

src/heap/spaces-inl.h

@@ -303,7 +303,9 @@ AllocationResult PagedSpace::AllocateRawDoubleAligned(int size_in_bytes) {
     if (object == NULL) {
       object = SlowAllocateRaw(aligned_size_in_bytes);
     }
-    object = heap()->EnsureDoubleAligned(object, aligned_size_in_bytes);
+    if (object != NULL) {
+      object = heap()->EnsureDoubleAligned(object, aligned_size_in_bytes);
+    }
   }
 
   if (object != NULL) {