Cherry-pick 5ec2341. rdar://problem/112439220

    Cherry-pick 266238@main (5ec2341). rdar://112439220

        Avoid creating a new CSSParserContext each time a color is assigned to fillStyle/strokeStyle on a canvas context
        https://bugs.webkit.org/show_bug.cgi?id=259431
        rdar://112439220

        Reviewed by Tim Nguyen.

        Creating the CSSParserContext is slightly expensive, since it fetches all of the relevant document Settings.

        * Source/WebCore/html/HTMLCanvasElement.h:
        (WebCore::HTMLCanvasElement::cssParserContext):
        * Source/WebCore/html/canvas/CanvasStyle.cpp:
        (WebCore::parseColor):

        Canonical link: https://commits.webkit.org/266238@main

Identifier: 265870.287@safari-7616.1.27.13-branch

Source/WebCore/html/HTMLCanvasElement.h

@@ -28,6 +28,7 @@
 #pragma once
 
 #include "ActiveDOMObject.h"
+#include "CSSParserContext.h"
 #include "CanvasBase.h"
 #include "Document.h"
 #include "FloatRect.h"
@@ -144,6 +145,7 @@ class HTMLCanvasElement final : public HTMLElement, public CanvasBase, public Ac
 
     using HTMLElement::ref;
     using HTMLElement::deref;
+    CSSParserContext& cssParserContext();
 
 private:
     HTMLCanvasElement(const QualifiedName&, Document&);
@@ -189,6 +191,7 @@ class HTMLCanvasElement final : public HTMLElement, public CanvasBase, public Ac
 
     std::unique_ptr<CanvasRenderingContext> m_context;
     mutable RefPtr<Image> m_copiedImage; // FIXME: This is temporary for platforms that have to copy the image buffer to render (and for CSSCanvasValue).
+    std::unique_ptr<CSSParserContext> m_cssParserContext;
 
     std::optional<bool> m_usesDisplayListDrawing;
 
@@ -203,6 +206,13 @@ class HTMLCanvasElement final : public HTMLElement, public CanvasBase, public Ac
     bool m_isSnapshotting { false };
 };
 
+inline CSSParserContext& HTMLCanvasElement::cssParserContext()
+{
+    if (!m_cssParserContext)
+        m_cssParserContext = WTF::makeUnique<CSSParserContext>(document());
+    return *m_cssParserContext;
+}
+
 WebCoreOpaqueRoot root(HTMLCanvasElement*);
 
 } // namespace WebCore

Source/WebCore/html/canvas/CanvasStyle.cpp

@@ -60,7 +60,7 @@ Color parseColor(const String& colorString, CanvasBase& canvasBase)
 
     Color color;
     if (is<HTMLCanvasElement>(canvasBase))
-        color = CSSParser::parseColor(colorString, CSSParserContext { downcast<HTMLCanvasElement>(canvasBase).document() });
+        color = CSSParser::parseColor(colorString, downcast<HTMLCanvasElement>(canvasBase).cssParserContext());
     else
         color = CSSParser::parseColorWithoutContext(colorString);