Track the region where text is painted.

Source/WebKit/chromium/src/WebFontImpl.cpp

Index: Source/WebKit/chromium/src/WebFontImpl.cpp
diff --git a/Source/WebKit/chromium/src/WebFontImpl.cpp b/Source/WebKit/chromium/src/WebFontImpl.cpp
index 6797602de90760fea8f4ffc9ca7c54039ccf2fe3..f14ac2691f02878644dcfb9cdd97dcd9c3c66b73 100644
--- a/Source/WebKit/chromium/src/WebFontImpl.cpp
+++ b/Source/WebKit/chromium/src/WebFontImpl.cpp
@@ -94,6 +94,11 @@ void WebFontImpl::drawText(WebCanvas* canvas, const WebTextRun& run, const WebFl
                            int from, int to) const
 {
     FontCachePurgePreventer fontCachePurgePreventer;
+    WebCore::FloatRect textClipRect(clip);
+    TextRunPaintInfo runInfo(run);
+    runInfo.from = from;
+    runInfo.to = to;
+    runInfo.bounds = textClipRect;
 
     GraphicsContextBuilder builder(canvas);
     GraphicsContext& gc = builder.context();
@@ -101,8 +106,8 @@ void WebFontImpl::drawText(WebCanvas* canvas, const WebTextRun& run, const WebFl
     gc.save();
     gc.setShouldSmoothFonts(canvasIsOpaque);
     gc.setFillColor(color, ColorSpaceDeviceRGB);
-    gc.clip(WebCore::FloatRect(clip));
-    m_font.drawText(&gc, run, leftBaseline, from, to);
+    gc.clip(textClipRect);
+    m_font.drawText(&gc, runInfo, leftBaseline);
     gc.restore();
 
 #if defined(WIN32)