[PM] Fix origin computation of about:blank frame nodes

An about:blank frame inherits its origin from its parent [1, 2].
This adjust the node aggregation type computation return
kSameOriginAggregationPoint in the case when
- the current frame is about:blank and
- its parent has the same origin as the requesting origin.

This change provides better results for pages that create and pool
many about:blank iframe for warming up.

[1]: https://html.spec.whatwg.org/multipage/browsers.html#determining-the-origin
[2]: https://developer.mozilla.org/en-US/docs/Web/Security/Same-origin_policy#inherited_origins

Bug: 1085129
Change-Id: Iffe6b09a6b8ec1e2fd7b9a293e4b714a955d95fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627492
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843649}

components/performance_manager/v8_memory/web_memory_aggregator.cc

@@ -32,8 +32,16 @@ bool ShouldFollowOpenerLink(const PageNode* page_node) {
 }
 
 // Returns |frame_node|'s origin based on its current url.
+// An about:blank iframe inherits the origin of its parent. See:
+// https://html.spec.whatwg.org/multipage/browsers.html#determining-the-origin
 url::Origin GetOrigin(const FrameNode* frame_node) {
-  return url::Origin::Create(frame_node->GetURL());
+  if (frame_node->GetParentFrameNode()) {
+    return url::Origin::Resolve(
+        frame_node->GetURL(),
+        url::Origin::Create(frame_node->GetParentFrameNode()->GetURL()));
+  } else {
+    return url::Origin::Create(frame_node->GetURL());
+  }
 }
 
 #if DCHECK_IS_ON()
@@ -152,8 +160,10 @@ WebMemoryAggregator::FindNodeAggregationType(const FrameNode* frame_node) {
     return NodeAggregationType::kInvisible;
   }
 
-  if (requesting_origin_.IsSameOriginWith(GetOrigin(parent_node)))
+  auto parent_origin = GetOrigin(parent_node);
+  if (requesting_origin_.IsSameOriginWith(parent_origin)) {
     return NodeAggregationType::kCrossOriginAggregationPoint;
+  }
 
   // Otherwise |frame_node|'s memory should be aggregated into the last
   // aggregation point.

components/performance_manager/v8_memory/web_memory_aggregator_unittest.cc

@@ -397,6 +397,39 @@ TEST_F(WebMemoryAggregatorTest, AggregateNestedCrossOrigin) {
   EXPECT_EQ(MeasurementToJSON(result), MeasurementToJSON(expected_result));
 }
 
+TEST_F(WebMemoryAggregatorTest, AggregateSameOriginAboutBlank) {
+  FrameNodeImpl* main_frame = AddFrameNode("https://example.com/", Bytes{10});
+  AddFrameNode("about:blank", Bytes{20}, main_frame);
+
+  auto expected_result = CreateExpectedMemoryMeasurement({
+      ExpectedMemoryBreakdown(10, AttributionScope::kWindow,
+                              "https://example.com/"),
+      ExpectedMemoryBreakdown(20, AttributionScope::kWindow, "about:blank"),
+  });
+  EXPECT_EQ(internal::FindAggregationStartNode(main_frame), main_frame);
+  WebMemoryAggregator aggregator(main_frame);
+  auto result = aggregator.AggregateMeasureMemoryResult();
+  EXPECT_EQ(MeasurementToJSON(result), MeasurementToJSON(expected_result));
+}
+
+TEST_F(WebMemoryAggregatorTest, SkipCrossOriginAboutBlank) {
+  FrameNodeImpl* main_frame = AddFrameNode("https://example.com/", Bytes{10});
+  FrameNodeImpl* cross_site_child =
+      AddFrameNode("https://foo.com/", Bytes{20}, main_frame);
+  AddFrameNode("about:blank", Bytes{30}, cross_site_child);
+
+  auto expected_result = CreateExpectedMemoryMeasurement({
+      ExpectedMemoryBreakdown(10, AttributionScope::kWindow,
+                              "https://example.com/"),
+      ExpectedMemoryBreakdown(50, AttributionScope::kCrossOriginAggregated,
+                              base::nullopt),
+  });
+  EXPECT_EQ(internal::FindAggregationStartNode(main_frame), main_frame);
+  WebMemoryAggregator aggregator(main_frame);
+  auto result = aggregator.AggregateMeasureMemoryResult();
+  EXPECT_EQ(MeasurementToJSON(result), MeasurementToJSON(expected_result));
+}
+
 TEST_F(WebMemoryAggregatorTest, FindAggregationStartNode) {
   FrameNodeImpl* main_frame = AddFrameNode("https://example.com/", Bytes{10});
   FrameNodeImpl* cross_site_child = AddFrameNode(