HostDiscardableSharedMemoryManager should store the default memory limit

content/common/host_discardable_shared_memory_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/common/host_discardable_shared_memory_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 146 matching lines @@
 }  // namespace
 
 HostDiscardableSharedMemoryManager::MemorySegment::MemorySegment(
     std::unique_ptr<base::DiscardableSharedMemory> memory)
     : memory_(std::move(memory)) {}
 
 HostDiscardableSharedMemoryManager::MemorySegment::~MemorySegment() {
 }
 
 HostDiscardableSharedMemoryManager::HostDiscardableSharedMemoryManager()
-    : memory_limit_(GetDefaultMemoryLimit()),
+    : default_memory_limit_(GetDefaultMemoryLimit()),

[bashi, 2016/10/04 03:13:10]

Though GetDefaultMemoryLimit() could be dynamically changed, I think using the
initial value as a default value makes sense because (1) the implementation is
simpler and (2) amount of free disk space isn't a primary metric.

+      memory_limit_(default_memory_limit_),
       bytes_allocated_(0),
       memory_pressure_listener_(new base::MemoryPressureListener(
           base::Bind(&HostDiscardableSharedMemoryManager::OnMemoryPressure,
                      base::Unretained(this)))),
       // Current thread might not have a task runner in tests.
       enforce_memory_policy_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       enforce_memory_policy_pending_(false),
       weak_ptr_factory_(this) {
   DCHECK_NE(memory_limit_, 0u);
   enforce_memory_policy_callback_ =
@@ skipping 167 matching lines @@
 size_t HostDiscardableSharedMemoryManager::GetBytesAllocated() {
   base::AutoLock lock(lock_);
 
   return bytes_allocated_;
 }
 
 void HostDiscardableSharedMemoryManager::OnMemoryStateChange(
     base::MemoryState state) {
   switch (state) {
     case base::MemoryState::NORMAL:
-      SetMemoryLimit(GetDefaultMemoryLimit());
+      SetMemoryLimit(default_memory_limit_);
       break;
     case base::MemoryState::THROTTLED:
       SetMemoryLimit(0);
       break;
     case base::MemoryState::SUSPENDED:
       // Note that SUSPENDED never occurs in the main browser process so far.
       // Fall through.
     case base::MemoryState::UNKNOWN:
       NOTREACHED();
       break;
@@ skipping 204 matching lines @@
     return;
 
   enforce_memory_policy_pending_ = true;
   DCHECK(enforce_memory_policy_task_runner_);
   enforce_memory_policy_task_runner_->PostDelayedTask(
       FROM_HERE, enforce_memory_policy_callback_,
       base::TimeDelta::FromMilliseconds(kEnforceMemoryPolicyDelayMs));
 }
 
 }  // namespace content