cc: Prevent the tile manager from allocating more memory than allowed.

cc/resources/resource_pool.h

Index: cc/resources/resource_pool.h
diff --git a/cc/resources/resource_pool.h b/cc/resources/resource_pool.h
index 309bf33f30b0873f50059780dae77efffdc0b0b3..1710a7fdaf652d1d08ded9b882632b5c8eb878b4 100644
--- a/cc/resources/resource_pool.h
+++ b/cc/resources/resource_pool.h
@@ -42,7 +42,9 @@ class CC_EXPORT ResourcePool {
 
   void SetMemoryUsageLimits(size_t max_memory_usage_bytes,
                             size_t max_unused_memory_usage_bytes,
-                            size_t num_resources_limit);
+                            size_t max_resource_count);
+
+  void ReduceMemoryUsage();
 
   size_t total_memory_usage_bytes() const {
     return memory_usage_bytes_;
@@ -50,7 +52,9 @@ class CC_EXPORT ResourcePool {
   size_t acquired_memory_usage_bytes() const {
     return memory_usage_bytes_ - unused_memory_usage_bytes_;
   }
-  size_t NumResources() const { return resources_.size(); }
+  size_t acquired_resource_count() const {
+    return resource_count_ - unused_resources_.size();
+  }
 
  protected:
   explicit ResourcePool(ResourceProvider* resource_provider);
@@ -61,12 +65,13 @@ class CC_EXPORT ResourcePool {
   ResourceProvider* resource_provider_;
   size_t max_memory_usage_bytes_;
   size_t max_unused_memory_usage_bytes_;
+  size_t max_resource_count_;
   size_t memory_usage_bytes_;
   size_t unused_memory_usage_bytes_;
-  size_t num_resources_limit_;
+  size_t resource_count_;
 
   typedef std::list<Resource*> ResourceList;
-  ResourceList resources_;
+  ResourceList unused_resources_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourcePool);
 };