PM: On-demand instantiate process data in FrozenFrameAggregator.

It's an eyesore that we're instantiating and describing this data
on non-renderer process nodes.

Bug: 1080647
Change-Id: I00ac8f6fc8732b66ffb42516c7d140113c7aa84a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218556Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Commit-Queue: Sigurður Ásgeirsson <siggi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772396}

chrome/browser/performance_manager/decorators/frozen_frame_aggregator.cc

@@ -158,11 +158,6 @@ void FrozenFrameAggregator::OnPageNodeAdded(const PageNode* page_node) {
   FrozenDataImpl::GetOrCreate(page_impl);
 }
 
-void FrozenFrameAggregator::OnProcessNodeAdded(
-    const ProcessNode* process_node) {
-  FrozenDataImpl::GetOrCreate(ProcessNodeImpl::FromNode(process_node));
-}
-
 base::Value FrozenFrameAggregator::DescribePageNodeData(
     const PageNode* node) const {
   FrozenDataImpl* data = FrozenDataImpl::Get(PageNodeImpl::FromNode(node));
@@ -227,7 +222,10 @@ void FrozenFrameAggregator::UpdateFrameCounts(FrameNodeImpl* frame_node,
   auto* page_node = frame_node->page_node();
   auto* process_node = frame_node->process_node();
   auto* page_data = FrozenDataImpl::Get(page_node);
-  auto* process_data = FrozenDataImpl::Get(process_node);
+  auto* process_data = FrozenDataImpl::GetOrCreate(process_node);
+
+  // We should only have frames attached to renderer processes.
+  DCHECK_EQ(content::PROCESS_TYPE_RENDERER, process_node->process_type());
 
   // Set the page lifecycle state based on the state of the frame tree.
   if (page_data->ChangeFrameCounts(current_frame_delta, frozen_frame_delta)) {

chrome/browser/performance_manager/decorators/frozen_frame_aggregator.h

@@ -47,9 +47,6 @@ class FrozenFrameAggregator : public FrameNode::ObserverDefaultImpl,
   // PageNodeObserver implementation:
   void OnPageNodeAdded(const PageNode* page_node) override;
 
-  // ProcessNodeObserver implementation:
-  void OnProcessNodeAdded(const ProcessNode* process_node) override;
-
   // NodeDataDescriber implementation:
   base::Value DescribePageNodeData(const PageNode* node) const override;
   base::Value DescribeProcessNodeData(const ProcessNode* node) const override;

chrome/browser/performance_manager/decorators/frozen_frame_aggregator_unittest.cc

@@ -68,6 +68,11 @@ class FrozenFrameAggregatorTest : public GraphTestHarness {
     ExpectData(process_node_.get(), current_frame_count, frozen_frame_count);
   }
 
+  void ExpectNoProcessData() {
+    EXPECT_EQ(nullptr,
+              FrozenFrameAggregator::Data::GetForTesting(process_node_.get()));
+  }
+
   void ExpectRunning() {
     EXPECT_EQ(LifecycleState::kRunning, page_node_.get()->lifecycle_state());
   }
@@ -94,11 +99,12 @@ TEST_F(FrozenFrameAggregatorTest, ProcessAggregation) {
   MockProcessNodeObserver obs;
   graph()->AddProcessNodeObserver(&obs);
 
-  ExpectProcessData(0, 0);
+  // The data should be created on first aggregation.
+  ExpectNoProcessData();
 
   // Add a main frame.
   auto f0 = CreateFrame(nullptr, 0);
-  ExpectProcessData(0, 0);
+  ExpectNoProcessData();
 
   // Make the frame current.
   f0.get()->SetIsCurrent(true);