TextBlob: Start caching a text blob per InlineTextBox.

Source/core/rendering/InlineTextBox.cpp

Index: Source/core/rendering/InlineTextBox.cpp
diff --git a/Source/core/rendering/InlineTextBox.cpp b/Source/core/rendering/InlineTextBox.cpp
index b1352fcb62c8278fb0873ae7de8e6ab011309024..a241b876332d27331ec49851d87bff335e1ba191 100644
--- a/Source/core/rendering/InlineTextBox.cpp
+++ b/Source/core/rendering/InlineTextBox.cpp
@@ -63,7 +63,7 @@ namespace blink {
 struct SameSizeAsInlineTextBox : public InlineBox {
     unsigned variables[1];
     unsigned short variables2[2];
-    void* pointers[2];
+    void* pointers[3];
 };
 
 COMPILE_ASSERT(sizeof(InlineTextBox) == sizeof(SameSizeAsInlineTextBox), InlineTextBox_should_stay_small);
@@ -588,7 +588,8 @@ void InlineTextBox::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset,
             startOffset = selectionEnd;
             endOffset = selectionStart;
         }
-        textPainter.paint(startOffset, endOffset, length, textStyle);
+        bool textBlobIsCacheable = RuntimeEnabledFeatures::textBlobEnabled() && startOffset == 0 && endOffset == length;
+        textPainter.paint(startOffset, endOffset, length, textStyle, textBlobIsCacheable ? &m_textBlobCache : 0);
     }
 
     if ((paintSelectedTextOnly || paintSelectedTextSeparately) && selectionStart < selectionEnd) {