[heap] make inline-allocation-observers precise

src/heap/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include "src/allocation.h"
 #include "src/atomic-utils.h"
 #include "src/base/atomicops.h"
@@ skipping 2495 matching lines @@
   // Last page returned.
   NewSpacePage* last_page_;
 };
 
 // -----------------------------------------------------------------------------
 // Allows observation of inline allocation in the new space.
 class InlineAllocationObserver {
  public:
   explicit InlineAllocationObserver(intptr_t step_size)
       : step_size_(step_size), bytes_to_next_step_(step_size) {
-    DCHECK(step_size >= kPointerSize && (step_size & kHeapObjectTagMask) == 0);
+    DCHECK(step_size >= kPointerSize);
   }
   virtual ~InlineAllocationObserver() {}
 
  private:
   intptr_t step_size() const { return step_size_; }
   intptr_t bytes_to_next_step() const { return bytes_to_next_step_; }
 
-  // Pure virtual method provided by the subclasses that gets called when more
-  // than step_size byte have been allocated.
+  // Pure virtual method provided by the subclasses that gets called when at
+  // least step_size byte have been allocated.

[Hannes Payer (out of office), 2015/11/17 14:41:30]

byte => bytes

   virtual void Step(int bytes_allocated) = 0;
 
   // Called each time the new space does an inline allocation step. This may be
   // more frequently than the step_size we are monitoring (e.g. when there are
   // multiple observers, or when page or space boundary is encountered.) The
-  // Step method is only called once more than step_size bytes have been
+  // Step method is only called once at least than step_size bytes have been

[Hannes Payer (out of office), 2015/11/17 14:41:30]

This sentence seems to be broken. Do we still need it?

   // allocated.
   void InlineAllocationStep(int bytes_allocated) {
     bytes_to_next_step_ -= bytes_allocated;
     if (bytes_to_next_step_ <= 0) {
       Step(static_cast<int>(step_size_ - bytes_to_next_step_));
       bytes_to_next_step_ = step_size_;
     }
   }
 
   intptr_t step_size_;
@@ skipping 582 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_