unified-heap: Enable per default

Enabling unfied heap garbage collections per default.

Bug: 843903
Change-Id: I473f85bbe2d6b3fc72051549ffd389896cc488c6
Reviewed-on: https://chromium-review.googlesource.com/c/1412026Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629116}

chrome/browser/apps/guest_view/web_view_browsertest.cc

@@ -3533,7 +3533,11 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, BasicPostMessage) {
 }
 
 // Tests that webviews do get garbage collected.
-IN_PROC_BROWSER_TEST_F(WebViewTest, Shim_TestGarbageCollect) {
+// This test is disabled because it relies on garbage collections triggered from
+// window.gc() to run precisely. This is not the case with unified heap where
+// they need to conservatively scan the stack, potentially keeping objects
+// alive. https://crbug.com/843903
+IN_PROC_BROWSER_TEST_F(WebViewTest, DISABLED_Shim_TestGarbageCollect) {
   TestHelper("testGarbageCollect", "web_view/shim", NO_TEST_SERVER);
   GetGuestViewManager()->WaitForSingleViewGarbageCollected();
 }

content/public/common/content_features.cc

@@ -68,7 +68,7 @@ const base::Feature kBlinkHeapIncrementalMarking{
 
 // Enable unified garbage collection in Blink.
 const base::Feature kBlinkHeapUnifiedGarbageCollection{
-    "BlinkHeapUnifiedGarbageCollection", base::FEATURE_DISABLED_BY_DEFAULT};
+    "BlinkHeapUnifiedGarbageCollection", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enable bloated renderer detection.
 const base::Feature kBloatedRendererDetection{

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -597,6 +597,7 @@
     },
     {
       name: "HeapUnifiedGarbageCollection",
+      status: "stable",
     },
     {
       name: "HrefTranslate",

third_party/blink/web_tests/fast/xpath/xpath-iterator-result-should-mark-its-nodeset-expected.txt

@@ -2,6 +2,6 @@ Test for bug 34231: Nodes in XPathResult should keep JS wrappers alive.
 For this test to PASS you should see 2 PASS below.
 
 
-undefined
-undefined
+PASS
+PASS
 

third_party/blink/web_tests/fast/xpath/xpath-other-nodeset-result-should-mark-its-nodeset-expected.txt

@@ -2,6 +2,6 @@ Test for bug 34231: Nodes in XPath result snapshots should keep JS wrappers aliv
 For this test to PASS you should see 2 PASS below.
 
 
-undefined
-undefined
+PASS
+PASS
 

third_party/blink/web_tests/fast/xpath/xpath-snapshot-result-should-mark-its-nodeset-expected.txt

@@ -2,6 +2,6 @@ Test for bug 34231: Nodes in XPath result snapshots should keep JS wrappers aliv
 For this test to PASS you should see 2 PASS below.
 
 
-undefined
-undefined
+PASS
+PASS