Merge "DeferredShaping: Do not auto-lock by selection, focus, etc." t…

…o M103 branch

This is a reland of commit ae4e1fc

Changes from the original CL:
 * Add null element_ check to IsShapingDeferred()
 * Add a test for the above.

Original change's description:
> DeferredShaping: Do not auto-lock by selection, focus, etc.
>
> After shapign-deferred boxes are unlocked automitically by selection,
> focus, etc., they should not be locked automatically again in order to
> avoid inconsistent locking states.
>
> Bug: 1328053
> Change-Id: I7ce01361be0c88d374f80082a2ce37a1817a768c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3666576
> Auto-Submit: Kent Tamura <tkent@chromium.org>
> Reviewed-by: Koji Ishii <kojii@chromium.org>
> Commit-Queue: Koji Ishii <kojii@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1007770}

(cherry picked from commit b815a2d)

Bug: 1328053, 1330060
Change-Id: Id19254e2e2dcc23531757e99d9022242d9bc963c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3675737
Auto-Submit: Kent Tamura <tkent@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1008725}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3680238
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5060@{#412}
Cr-Branched-From: b83393d-refs/heads/main@{#1002911}

third_party/blink/renderer/core/display_lock/display_lock_context.cc

@@ -923,6 +923,8 @@ void DisplayLockContext::ScheduleTopLayerCheck() {
 }
 
 bool DisplayLockContext::IsShapingDeferred() const {
+  if (!element_)
+    return false;
   if (const auto* layout_object = element_->GetLayoutObject())
     return layout_object->IsShapingDeferred();
   return false;
@@ -1218,6 +1220,17 @@ void DisplayLockContext::NotifyRenderAffectingStateChanged() {
         !state(RenderAffectingState::kAutoUnlockedForPrint) &&
         !state(RenderAffectingState::kSubtreeHasTopLayerElement)));
 
+  // For shaping-deferred boxes, we'd like to unlock permanently.
+  if (IsShapingDeferred() && state_ != EContentVisibility::kVisible &&
+      !should_be_locked && IsLocked()) {
+    SetRequestedState(EContentVisibility::kVisible);
+    // We need to change the document lifecycle explicitly because Unlock()
+    // inside the above SetRequestedState() didn't change the lifecycle.
+    // See CanDirtyStyle() check in Unlock().
+    document_->Lifecycle().EnsureStateAtMost(DocumentLifecycle::kStyleClean);
+    return;
+  }
+
   if (should_be_locked && !IsLocked())
     Lock();
   else if (!should_be_locked && IsLocked())

third_party/blink/renderer/core/layout/deferred_shaping_test.cc

@@ -12,6 +12,7 @@
 #include "third_party/blink/renderer/core/paint/paint_timing.h"
 #include "third_party/blink/renderer/core/testing/core_unit_test_helper.h"
 #include "third_party/blink/renderer/platform/fonts/shaping/shape_result_inline_headers.h"
+#include "third_party/blink/renderer/platform/heap/thread_state.h"
 #include "third_party/blink/renderer/platform/testing/runtime_enabled_features_test_helpers.h"
 
 namespace blink {
@@ -158,6 +159,46 @@ TEST_F(DeferredShapingTest, DynamicPropertyChange) {
   EXPECT_TRUE(IsLocked("target"));
 }
 
+TEST_F(DeferredShapingTest, NoAutoLock) {
+  SetBodyInnerHTML(R"HTML(
+<div style="height:1800px"></div>
+<div id="target">IFC</div>
+)HTML");
+  UpdateAllLifecyclePhasesForTest();
+  EXPECT_TRUE(IsDefer("target"));
+  EXPECT_TRUE(IsLocked("target"));
+
+  auto* context = GetElementById("target")->GetDisplayLockContext();
+  context->NotifySubtreeGainedSelection();
+  EXPECT_FALSE(IsLocked("target"));
+
+  context->NotifySubtreeLostSelection();
+  EXPECT_FALSE(IsLocked("target"));
+}
+
+// crbug.com/1330060
+TEST_F(DeferredShapingTest, NoAutoLockWithoutElement) {
+  SetBodyInnerHTML(R"HTML(
+<div style="height:1800px"></div>
+<div id="target">IFC</div>
+)HTML");
+  UpdateAllLifecyclePhasesForTest();
+  EXPECT_TRUE(IsDefer("target"));
+  EXPECT_TRUE(IsLocked("target"));
+
+  Persistent<DisplayLockContext> context =
+      GetElementById("target")->GetDisplayLockContext();
+  context->NotifySubtreeGainedSelection();
+  EXPECT_FALSE(IsLocked("target"));
+
+  GetElementById("target")->remove();
+  UpdateAllLifecyclePhasesForTest();
+  // Clear a WeakMember of DisplayLockContext.
+  ThreadState::Current()->CollectAllGarbageForTesting();
+  context->NotifySubtreeLostSelection();
+  // Pass if no crashes.
+}
+
 TEST_F(DeferredShapingTest, ListMarkerCrash) {
   SetBodyInnerHTML(R"HTML(
 <div style="height:1800px"></div>