Let FrameSelection::localCaretRect on a text input field avoid synchronous layout.

Source/core/editing/PositionWithAffinity.cpp

Index: Source/core/editing/PositionWithAffinity.cpp
diff --git a/Source/core/editing/PositionWithAffinity.cpp b/Source/core/editing/PositionWithAffinity.cpp
index 668c408b2f6810f9070bb40f3bfa3a69c9de4815..4f380394e07e4294837db3775c0dd80e1dc5d631 100644
--- a/Source/core/editing/PositionWithAffinity.cpp
+++ b/Source/core/editing/PositionWithAffinity.cpp
@@ -4,6 +4,7 @@
 
 #include "config.h"
 #include "core/editing/PositionWithAffinity.h"
+#include "core/rendering/InlineBox.h"
 
 namespace blink {
 
@@ -22,6 +23,28 @@ PositionWithAffinity::~PositionWithAffinity()
 {
 }
 
+LayoutRect PositionWithAffinity::localCaretRect(RenderObject*& renderer) const

[yosin_UTC9, 2014/07/29 07:00:20]

It seems we can return just renderer and computing local caret rect on call
sites.

[yoichio, 2014/07/29 08:05:17]

calling localCaretRect uses local variables |inlineBox| and |caretOffset| so it
is not simple.

+{
+    if (m_position.isNull()) {
+        renderer = 0;

[yosin_UTC9, 2014/07/29 07:00:20]

nit: Let's use |nullptr|.

[yoichio, 2014/07/29 08:05:17]

Done.

+        return IntRect();
+    }
+    Node* node = m_position.anchorNode();
+
+    renderer = node->renderer();
+    if (!renderer)
+        return LayoutRect();
+
+    InlineBox* inlineBox;
+    int caretOffset;
+    m_position.getInlineBoxAndOffset(m_affinity, inlineBox, caretOffset);
+
+    if (inlineBox)
+        renderer = &inlineBox->renderer();
+
+    return renderer->localCaretRect(inlineBox, caretOffset);
+}
+
 void PositionWithAffinity::trace(Visitor* visitor)
 {
     visitor->trace(m_position);