Convert renderer JS memory usage reporting to use Mojo.

chrome/browser/process_resource_usage.cc

Index: chrome/browser/process_resource_usage.cc
diff --git a/chrome/browser/process_resource_usage.cc b/chrome/browser/process_resource_usage.cc
index f892ade2f1f2a42d4093c2dba2de2c6058b8c2d3..3eee701f179ada640c28a75dc76052b17677712b 100644
--- a/chrome/browser/process_resource_usage.cc
+++ b/chrome/browser/process_resource_usage.cc
@@ -5,19 +5,38 @@
 #include "chrome/browser/process_resource_usage.h"
 
 #include "base/bind.h"
+#include "base/location.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop_proxy.h"
 
 ProcessResourceUsage::ProcessResourceUsage(ResourceUsageReporterPtr service)
     : service_(service.Pass()), update_in_progress_(false) {
+  service_.set_error_handler(this);
 }
 
 ProcessResourceUsage::~ProcessResourceUsage() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
-void ProcessResourceUsage::Refresh() {
+void ProcessResourceUsage::RunPendingRefreshCallbacks() {
+  auto message_loop = base::MessageLoopProxy::current();
+  for (const auto& callback : refresh_callbacks_)
+    message_loop->PostTask(FROM_HERE, callback);
+  refresh_callbacks_.clear();
+}
+
+void ProcessResourceUsage::Refresh(const base::Closure& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  if (!update_in_progress_ && service_) {
+  if (!service_ || service_.encountered_error()) {
+    if (!callback.is_null())
+      base::MessageLoopProxy::current()->PostTask(FROM_HERE, callback);
+    return;
+  }
+
+  if (!callback.is_null())
+    refresh_callbacks_.push_back(callback);
+
+  if (!update_in_progress_) {
     update_in_progress_ = true;
     service_->GetUsageData(base::Bind(&ProcessResourceUsage::OnRefreshDone,
                                       base::Unretained(this)));
@@ -28,6 +47,12 @@ void ProcessResourceUsage::OnRefreshDone(ResourceUsageDataPtr data) {
   DCHECK(thread_checker_.CalledOnValidThread());
   update_in_progress_ = false;
   stats_ = data.Pass();
+  RunPendingRefreshCallbacks();
+}
+
+void ProcessResourceUsage::OnConnectionError() {

[ncarter (slow), 2015/05/14 06:28:12]

Does it make sense to zero the |stats_| when the child process dies?

[Anand Mistry (off Chromium), 2015/05/14 07:30:41]

I honestly have no idea. Maybe we want to keep the last known information. Maybe
expose an "IsAlive()" instead, but right now, I don't think there's a use for
it. Since this only affects the task manager (memory-internals will create a new
one for each update), this question is, what do you want to see in the task
manager?

[ncarter (slow), 2015/05/14 13:59:58]

You can leave it as is. The task manager removes rows as soon as it knows
they've crashed, so I agree it's a moot point.

+  DCHECK(thread_checker_.CalledOnValidThread());
+  RunPendingRefreshCallbacks();
 }
 
 bool ProcessResourceUsage::ReportsV8MemoryStats() const {