Compile core/dom/ with -Wshadow.

Bug: 294205
Change-Id: I63ccd3a15d31ab2633b874193fe26c24628bff81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2460891Reviewed-by: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815671}

third_party/blink/renderer/core/dom/BUILD.gn

@@ -27,6 +27,8 @@ import("//third_party/blink/renderer/core/core.gni")
 # -O2 optimiziation. If there is common inlined implementations, put this in
 # foo-inl.h and include that in both foo.cc and foo-hot.cc.
 blink_core_sources("dom_hotpath") {
+  configs += [ "//build/config/compiler:noshadowing" ]
+
   sources = [
     "element-hot.cc",
     "element-inl.h",
@@ -41,6 +43,8 @@ blink_core_sources("dom_hotpath") {
 }
 
 blink_core_sources("dom") {
+  configs += [ "//build/config/compiler:noshadowing" ]
+
   sources = [
     "abort_controller.cc",
     "abort_controller.h",

third_party/blink/renderer/core/dom/document.cc

@@ -3877,8 +3877,8 @@ static bool AllDescendantsAreComplete(Document* document) {
       return false;
   }
   for (PortalContents* portal : DocumentPortals::From(*document).GetPortals()) {
-    auto* frame = portal->GetFrame();
-    if (frame && frame->IsLoading())
+    auto* portal_frame = portal->GetFrame();
+    if (portal_frame && portal_frame->IsLoading())
       return false;
   }
   return true;
@@ -5337,13 +5337,13 @@ Element* Document::SequentialFocusNavigationStartingPoint(
     if (type == mojom::blink::FocusType::kForward) {
       Node* previous = FlatTreeTraversal::Previous(*next_node);
       for (; previous; previous = FlatTreeTraversal::Previous(*previous)) {
-        if (auto* element = DynamicTo<Element>(previous))
-          return element;
+        if (auto* previous_element = DynamicTo<Element>(previous))
+          return previous_element;
       }
     }
     for (Node* next = next_node; next; next = FlatTreeTraversal::Next(*next)) {
-      if (auto* element = DynamicTo<Element>(next))
-        return element;
+      if (auto* next_element = DynamicTo<Element>(next))
+        return next_element;
     }
   }
   return nullptr;