Defer SVG text metrics rebuilding from style changes until layout

This patch removes LayoutSVGText::subtreeStyleDidChange which was
added in [1] to fix a font face crash. We no longer support SVG fonts
and subtreeStyleDidChange should never have been called on every layout
in the first place.

With this patch we mark LayoutSVGText as needing a text metrics update
when a child inline's style changes, and recalculate the text metrics
during layout.

This patch results in a 45% improvement on the SVGCubics benchmark
which is the heaviest SVG text benchmark we have.

[1] https://src.chromium.org/viewvc/blink?revision=167993&view=revision

BUG=589525

Review URL: https://codereview.chromium.org/1770663002

Cr-Commit-Position: refs/heads/master@{#379566}
(cherry picked from commit d0ffb54118db1b76565dd6d3ffe7623227663038)

Review URL: https://codereview.chromium.org/1809203004 .

Cr-Commit-Position: refs/branch-heads/2623@{#632}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}

3 files changed, 3 insertions, 20 deletions

diff --git a/third_party/WebKit/Source/core/layout/svg/LayoutSVGInlineText.cpp b/third_party/WebKit/Source/core/layout/svg/LayoutSVGInlineText.cpp
index 5243c2c..b78cebe 100644
--- a/third_party/WebKit/Source/core/layout/svg/LayoutSVGInlineText.cpp
+++ b/third_party/WebKit/Source/core/layout/svg/LayoutSVGInlineText.cpp
@@ -96,8 +96,10 @@ void LayoutSVGInlineText::styleDidChange(StyleDifference diff, const ComputedSty
         return;
 
     // The text metrics may be influenced by style changes.
-    if (LayoutSVGText* textLayoutObject = LayoutSVGText::locateLayoutSVGTextAncestor(this))
+    if (LayoutSVGText* textLayoutObject = LayoutSVGText::locateLayoutSVGTextAncestor(this)) {
+        textLayoutObject->setNeedsTextMetricsUpdate();
         textLayoutObject->setNeedsLayoutAndFullPaintInvalidation(LayoutInvalidationReason::StyleChange);
+    }
 }
 
 InlineTextBox* LayoutSVGInlineText::createTextBox(int start, unsigned short length)
diff --git a/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.cpp b/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.cpp
index cc7ad13..1ef39af 100644
--- a/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.cpp
+++ b/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.cpp
@@ -263,22 +263,6 @@ void LayoutSVGText::subtreeChildWasRemoved(const Vector<SVGTextLayoutAttributes*
         m_layoutAttributesBuilder.buildLayoutAttributesForText(affectedAttributes[i]->context());
 }
 
-void LayoutSVGText::subtreeStyleDidChange()
-{
-    if (!shouldHandleSubtreeMutations() || documentBeingDestroyed())
-        return;
-
-    checkLayoutAttributesConsistency(this, m_layoutAttributes);
-
-    // Only update the metrics cache, but not the text positioning element cache
-    // nor the layout attributes cached in the leaf #text layoutObjects.
-    FontCachePurgePreventer fontCachePurgePreventer;
-    for (LayoutObject* descendant = firstChild(); descendant; descendant = descendant->nextInPreOrder(this)) {
-        if (descendant->isSVGInlineText())
-            m_layoutAttributesBuilder.rebuildMetricsForTextLayoutObject(toLayoutSVGInlineText(descendant));
-    }
-}
-
 void LayoutSVGText::subtreeTextDidChange(LayoutSVGInlineText* text)
 {
     ASSERT(text);
@@ -319,8 +303,6 @@ void LayoutSVGText::layout()
     ASSERT(needsLayout());
     LayoutAnalyzer::Scope analyzer(*this);
 
-    subtreeStyleDidChange();
-
     bool updateCachedBoundariesInParents = false;
     if (m_needsTransformUpdate) {
         m_localTransform = toSVGTextElement(node())->calculateAnimatedLocalTransform();
diff --git a/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.h b/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.h
index fde5c84..566aba3 100644
--- a/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.h
+++ b/third_party/WebKit/Source/core/layout/svg/LayoutSVGText.h
@@ -54,7 +54,6 @@ public:
     void subtreeChildWasAdded(LayoutObject*);
     void subtreeChildWillBeRemoved(LayoutObject*, Vector<SVGTextLayoutAttributes*, 2>& affectedAttributes);
     void subtreeChildWasRemoved(const Vector<SVGTextLayoutAttributes*, 2>& affectedAttributes);
-    void subtreeStyleDidChange();
     void subtreeTextDidChange(LayoutSVGInlineText*);
 
     const AffineTransform& localToParentTransform() const override { return m_localTransform; }