Use DiscardableMemoryManager on Android.

base/memory/discardable_memory_manager_unittest.cc

Index: base/memory/discardable_memory_manager_unittest.cc
diff --git a/base/memory/discardable_memory_manager_unittest.cc b/base/memory/discardable_memory_manager_unittest.cc
index 58a9603ec86354685ac613199e204cd027deff7e..af7b3b34fef456d345085bacf8fd23bd6dabe2db 100644
--- a/base/memory/discardable_memory_manager_unittest.cc
+++ b/base/memory/discardable_memory_manager_unittest.cc
@@ -15,7 +15,7 @@ namespace {
 
 class TestAllocationImpl : public internal::DiscardableMemoryManagerAllocation {
  public:
-  TestAllocationImpl() : is_allocated_(false), is_locked_(false) {}
+  TestAllocationImpl() : is_allocated_(false), is_locked_(false), bytes_(0) {}
   virtual ~TestAllocationImpl() { DCHECK(!is_locked_); }
 
   // Overridden from internal::DiscardableMemoryManagerAllocation:
@@ -24,15 +24,19 @@ class TestAllocationImpl : public internal::DiscardableMemoryManagerAllocation {
     is_allocated_ = true;
     DCHECK(!is_locked_);
     is_locked_ = true;
+    DCHECK(!bytes_ || bytes_ == bytes);

[reveman, 2014/04/26 00:13:37]

how about we remove the |bytes| parameter from AllocateAndAcquireLock instead?

[Philippe, 2014/04/28 12:23:14]

Good idea, I was tempted to make the change too.

+    bytes_ = bytes;
     return was_allocated;
   }
   virtual void ReleaseLock() OVERRIDE {
-    DCHECK(is_locked_);
+    DCHECK_EQ(is_locked_, is_allocated_);

[reveman, 2014/04/26 00:13:37]

hm, this seems unnecessary. What sequence of events does this cover that was not
covered before?

[Philippe, 2014/04/28 12:23:14]

I think this was needed for the zero allocation (with my changes in Unregister()
though). I have now reverted my changes in the manager though.

     is_locked_ = false;
   }
   virtual void Purge() OVERRIDE {
-    DCHECK(is_allocated_);
+    // Allocation only happens for non-zero sizes.
+    DCHECK_EQ(is_allocated_, !!bytes_);
     is_allocated_ = false;
+    bytes_ = 0;
   }
 
   bool is_locked() const { return is_locked_; }
@@ -40,6 +44,7 @@ class TestAllocationImpl : public internal::DiscardableMemoryManagerAllocation {
  private:
   bool is_allocated_;
   bool is_locked_;
+  size_t bytes_;
 };
 
 class DiscardableMemoryManagerTestBase {