[heap] Make aligned allocations in black areas completely black.

BUG=

Review-Url: https://codereview.chromium.org/2591433002
Cr-Commit-Position: refs/heads/master@{#41814}

src/heap/spaces-inl.h

@@ -471,18 +471,20 @@ AllocationResult PagedSpace::AllocateRawAligned(int size_in_bytes,
     object = free_list_.Allocate(allocation_size);
     if (object == NULL) {
       object = SlowAllocateRaw(allocation_size);
-      if (object != NULL && heap()->incremental_marking()->black_allocation()) {
+    }
+    if (object != NULL) {
+      if (heap()->incremental_marking()->black_allocation()) {
         Address start = object->address();
-        Address end = object->address() + size_in_bytes;
+        Address end = object->address() + allocation_size;
         Page::FromAllocationAreaAddress(start)->CreateBlackArea(start, end);
       }
-    }
-    if (object != NULL && filler_size != 0) {
-      object = heap()->AlignWithFiller(object, size_in_bytes, allocation_size,
-                                       alignment);
-      // Filler objects are initialized, so mark only the aligned object memory
-      // as uninitialized.
-      allocation_size = size_in_bytes;
+      if (filler_size != 0) {
+        object = heap()->AlignWithFiller(object, size_in_bytes, allocation_size,
+                                         alignment);
+        // Filler objects are initialized, so mark only the aligned object
+        // memory as uninitialized.
+        allocation_size = size_in_bytes;
+      }
     }
   }