Refactor ContainerNode::GetUpperLeftCorner

This patch reorganizes the branches in the above mentioned function
to make the branching logic more clearer. It also contains some other
minor cleanup.

Bug: 
Change-Id: Iabe6c4fa4f6b2681dcb6b0c2cbc41f4a3382dcfa
Reviewed-on: https://chromium-review.googlesource.com/775892Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517339}

third_party/WebKit/Source/core/dom/ContainerNode.cpp

@@ -988,6 +988,7 @@ bool ContainerNode::GetUpperLeftCorner(FloatPoint& point) const {
     return false;
 
   // FIXME: What is this code really trying to do?
+  // TODO(xiaochengh): Rename |o| to |runner|.
   LayoutObject* o = GetLayoutObject();
   if (!o->IsInline() || o->IsAtomicInlineLevel()) {
     point = o->LocalToAbsolute(FloatPoint(), kUseTransforms);
@@ -996,7 +997,7 @@ bool ContainerNode::GetUpperLeftCorner(FloatPoint& point) const {
 
   // Find the next text/image child, to get a position.
   while (o) {
-    LayoutObject* p = o;
+    const LayoutObject* const previous = o;
     if (LayoutObject* o_first_child = o->SlowFirstChild()) {
       o = o_first_child;
     } else if (o->NextSibling()) {
@@ -1019,27 +1020,31 @@ bool ContainerNode::GetUpperLeftCorner(FloatPoint& point) const {
       return true;
     }
 
-    DCHECK(CanUseInlineBox(*o));
-    if (p->GetNode() && p->GetNode() == this && o->IsText() && !o->IsBR() &&
-        !ToLayoutText(o)->HasTextBoxes()) {
-      // Do nothing - skip unrendered whitespace that is a child or next sibling
-      // of the anchor.
-      // FIXME: This fails to skip a whitespace sibling when there was also a
-      // whitespace child (because p has moved).
-    } else if ((o->IsText() && !o->IsBR()) || o->IsAtomicInlineLevel()) {
+    if (o->IsText() && !o->IsBR()) {
+      if (previous->GetNode() == this && !ToLayoutText(o)->HasTextBoxes()) {
+        // Do nothing - skip unrendered whitespace that is a child or next
+        // sibling of the anchor.
+        // FIXME: This fails to skip a whitespace sibling when there was also a
+        // whitespace child (because |previous| has moved).
+        continue;
+      }
+      // TODO(xiaochengh): Move the code below to LayoutText.
+      DCHECK(CanUseInlineBox(*o));
       point = FloatPoint();
-      if (o->IsText()) {
-        if (ToLayoutText(o)->FirstTextBox())
-          point.Move(
-              ToLayoutText(o)->LinesBoundingBox().X(),
-              ToLayoutText(o)->FirstTextBox()->Root().LineTop().ToFloat());
-        point = o->LocalToAbsolute(point, kUseTransforms);
-      } else {
-        DCHECK(o->IsBox());
-        LayoutBox* box = ToLayoutBox(o);
-        point.MoveBy(box->Location());
-        point = o->Container()->LocalToAbsolute(point, kUseTransforms);
+      if (ToLayoutText(o)->FirstTextBox()) {
+        point.Move(ToLayoutText(o)->LinesBoundingBox().X(),
+                   ToLayoutText(o)->FirstTextBox()->Root().LineTop().ToFloat());
       }
+      point = o->LocalToAbsolute(point, kUseTransforms);
+      return true;
+    }
+
+    if (o->IsAtomicInlineLevel()) {
+      point = FloatPoint();
+      DCHECK(o->IsBox());
+      LayoutBox* box = ToLayoutBox(o);
+      point.MoveBy(box->Location());
+      point = o->Container()->LocalToAbsolute(point, kUseTransforms);
       return true;
     }
   }