[Experiment] purge-and-suspend

cc/raster/staging_buffer_pool.cc

Index: cc/raster/staging_buffer_pool.cc
diff --git a/cc/raster/staging_buffer_pool.cc b/cc/raster/staging_buffer_pool.cc
index 99fb43843105ece60a3ac000cbd3236ce601c003..5885394c9fa939f7bb76da8c26e881d0cdba484d 100644
--- a/cc/raster/staging_buffer_pool.cc
+++ b/cc/raster/staging_buffer_pool.cc
@@ -6,6 +6,7 @@
 
 #include <memory>
 
+#include "base/allocator/allocator_extension.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -141,6 +142,9 @@ StagingBufferPool::StagingBufferPool(base::SequencedTaskRunner* task_runner,
       this, "cc::StagingBufferPool", base::ThreadTaskRunnerHandle::Get());
   reduce_memory_usage_callback_ = base::Bind(
       &StagingBufferPool::ReduceMemoryUsage, weak_ptr_factory_.GetWeakPtr());
+
+  memory_pressure_listener_.reset(new base::MemoryPressureListener(base::Bind(
+      &StagingBufferPool::OnMemoryPressure, base::Unretained(this))));
 }
 
 StagingBufferPool::~StagingBufferPool() {
@@ -186,6 +190,16 @@ bool StagingBufferPool::OnMemoryDump(
   return true;
 }
 
+void StagingBufferPool::OnMemoryPressure(
+    base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
+  base::AutoLock lock(lock_);
+  if (buffers_.empty())
+    return;
+
+  ReleaseBuffersNotUsedSince(base::TimeTicks() + base::TimeDelta::Max());
+  base::allocator::ReleaseFreeMemory();
+}
+
 void StagingBufferPool::AddStagingBuffer(const StagingBuffer* staging_buffer,
                                          ResourceFormat format) {
   lock_.AssertAcquired();