Use new Traversal<*Element> API in svg code for clarity

Use new Traversal<*Element> API in svg code for clarity. It results in shorter /
simpler code. It also makes it clearer what type of Element we are actually
interested in.

R=
BUG=346733

Review URL: https://codereview.chromium.org/205983004

git-svn-id: svn://svn.chromium.org/blink/trunk@169621 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/svg/SVGElement.cpp

@@ -753,11 +753,9 @@ void SVGElement::collectStyleForPresentationAttribute(const QualifiedName& name,
 
 bool SVGElement::haveLoadedRequiredResources()
 {
-    Node* child = firstChild();
-    while (child) {
-        if (child->isSVGElement() && !toSVGElement(child)->haveLoadedRequiredResources())
+    for (SVGElement* child = Traversal<SVGElement>::firstChild(*this); child; child = Traversal<SVGElement>::nextSibling(*child)) {
+        if (!child->haveLoadedRequiredResources())
             return false;
-        child = child->nextSibling();
     }
     return true;
 }

third_party/WebKit/Source/core/svg/SVGSVGElement.cpp

@@ -30,7 +30,6 @@
 #include "core/css/CSSHelper.h"
 #include "core/dom/Document.h"
 #include "core/dom/ElementTraversal.h"
-#include "core/dom/NodeTraversal.h"
 #include "core/dom/StaticNodeList.h"
 #include "core/editing/FrameSelection.h"
 #include "core/events/EventListener.h"
@@ -825,11 +824,7 @@ Element* SVGSVGElement::getElementById(const AtomicString& id) const
 
     // Fall back to traversing our subtree. Duplicate ids are allowed, the first found will
     // be returned.
-    for (Node* node = firstChild(); node; node = NodeTraversal::next(*node, this)) {
-        if (!node->isElementNode())
-            continue;
-
-        Element* element = toElement(node);
+    for (Element* element = ElementTraversal::firstWithin(*this); element; element = ElementTraversal::next(*element, this)) {
         if (element->getIdAttribute() == id)
             return element;
     }

third_party/WebKit/Source/core/svg/SVGUseElement.cpp

@@ -580,13 +580,9 @@ void SVGUseElement::buildInstanceTree(SVGElement* target, SVGElementInstance* ta
     // is the SVGGElement object for the 'g', and then two child SVGElementInstance objects, each of which has
     // its correspondingElement that is an SVGRectElement object.
 
-    for (Node* node = target->firstChild(); node; node = node->nextSibling()) {
-        SVGElement* element = 0;
-        if (node->isSVGElement())
-            element = toSVGElement(node);
-
-        // Skip any non-svg nodes or any disallowed element.
-        if (!element || isDisallowedElement(element))
+    for (SVGElement* element = Traversal<SVGElement>::firstChild(*target); element; element = Traversal<SVGElement>::nextSibling(*element)) {
+        // Skip any disallowed element.
+        if (isDisallowedElement(element))
             continue;
 
         // Create SVGElementInstance object, for both container/non-container nodes.
@@ -820,17 +816,10 @@ void SVGUseElement::associateInstancesWithShadowTreeElements(Node* target, SVGEl
     targetInstance->setShadowTreeElement(element);
     element->setCorrespondingElement(originalElement);
 
-    Node* node = target->firstChild();
-    for (SVGElementInstance* instance = targetInstance->firstChild(); node && instance; instance = instance->nextSibling()) {
-        // Skip any non-svg elements in shadow tree
-        while (node && !node->isSVGElement())
-           node = node->nextSibling();
-
-        if (!node)
-            break;
-
-        associateInstancesWithShadowTreeElements(node, instance);
-        node = node->nextSibling();
+    SVGElement* child = Traversal<SVGElement>::firstChild(*target);
+    for (SVGElementInstance* instance = targetInstance->firstChild(); child && instance; instance = instance->nextSibling()) {
+        associateInstancesWithShadowTreeElements(child, instance);
+        child = Traversal<SVGElement>::nextSibling(*child);
     }
 }