Add GetStubStats and related functions in GpuMemoryManager.

content/common/gpu/gpu_memory_manager.cc

Index: content/common/gpu/gpu_memory_manager.cc
diff --git a/content/common/gpu/gpu_memory_manager.cc b/content/common/gpu/gpu_memory_manager.cc
index 212b50d0ed90656e91aa3155a9d7695638f7ca89..059c067d7f1da18ab5f3ece18ed31032260be178 100644
--- a/content/common/gpu/gpu_memory_manager.cc
+++ b/content/common/gpu/gpu_memory_manager.cc
@@ -63,7 +63,8 @@ GpuMemoryManager::GpuMemoryManager(GpuMemoryManagerClient* client,
     : client_(client),
       manage_immediate_scheduled_(false),
       max_surfaces_with_frontbuffer_soft_limit_(
-          max_surfaces_with_frontbuffer_soft_limit) {
+          max_surfaces_with_frontbuffer_soft_limit),
+      peak_assigned_allocation_sum_(0) {
 }
 
 GpuMemoryManager::~GpuMemoryManager() {
@@ -103,6 +104,11 @@ void GpuMemoryManager::ScheduleManage(bool immediate) {
   }
 }
 
+size_t GpuMemoryManager::GetAvailableGpuMemory() const {
+  // TODO(mmocny): Implement this with real system figures.
+  return kMaximumAllocationForTabs;
+}
+
 // The current Manage algorithm simply classifies contexts (stubs) into
 // "foreground", "background", or "hibernated" categories.
 // For each of these three categories, there are predefined memory allocation