Use IsEmpty for map keys.

And a small refactoring for readability of finding an xhr breakpoint.

I introduced IsEmpty in this PR:
https://chromium-review.googlesource.com/c/chromium/src/+/1154038

Change-Id: I7b02c9d4d4ae1e051688790f5043d8710cf1c692
Reviewed-on: https://chromium-review.googlesource.com/1154190Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579495}

third_party/blink/renderer/core/inspector/inspector_dom_debugger_agent.cc

@@ -711,20 +711,20 @@ Response InspectorDOMDebuggerAgent::removeXHRBreakpoint(const String& url) {
   return Response::OK();
 }
 
-void InspectorDOMDebuggerAgent::WillSendXMLHttpOrFetchNetworkRequest(
-    const String& url) {
-  String breakpoint_url;
-  if (pause_on_all_xhrs_.Get()) {
-    breakpoint_url = "";
-  } else {
+// Returns the breakpoint url if a match is found, or WTF::String().
+String InspectorDOMDebuggerAgent::MatchXHRBreakpoints(const String& url) const {
+  if (pause_on_all_xhrs_.Get())
+    return "";
   for (const WTF::String& breakpoint : xhr_breakpoints_.Keys()) {
-      if (url.Contains(breakpoint)) {
-        breakpoint_url = breakpoint;
-        break;
-      }
-    }
+    if (url.Contains(breakpoint))
+      return breakpoint;
   }
+  return WTF::String();
+}
 
+void InspectorDOMDebuggerAgent::WillSendXMLHttpOrFetchNetworkRequest(
+    const String& url) {
+  String breakpoint_url = MatchXHRBreakpoints(url);
   if (breakpoint_url.IsNull())
     return;
 
@@ -754,9 +754,9 @@ void InspectorDOMDebuggerAgent::DidAddBreakpoint() {
 void InspectorDOMDebuggerAgent::DidRemoveBreakpoint() {
   if (!dom_breakpoints_.IsEmpty())
     return;
-  if (!event_listener_breakpoints_.Keys().empty())
+  if (!event_listener_breakpoints_.IsEmpty())
     return;
-  if (!xhr_breakpoints_.Keys().empty())
+  if (!xhr_breakpoints_.IsEmpty())
     return;
   if (pause_on_all_xhrs_.Get())
     return;

third_party/blink/renderer/core/inspector/inspector_dom_debugger_agent.h

@@ -133,6 +133,8 @@ class CORE_EXPORT InspectorDOMDebuggerAgent final
       const v8_inspector::StringView& object_group_id);
 
  private:
+  String MatchXHRBreakpoints(const String& url) const;
+
   static void EventListenersInfoForTarget(v8::Isolate*,
                                           v8::Local<v8::Value>,
                                           int depth,