<webview>: Partially migrate loadcommit event from content to chrome

chrome/browser/webview/webview_constants.cc

Index: chrome/browser/webview/webview_constants.cc
diff --git a/chrome/browser/webview/webview_constants.cc b/chrome/browser/webview/webview_constants.cc
index 5a5e13b298383a019382b348f3691b18bacd91e5..d612ad9b150be4edc791b48e6e06df5091a47393 100644
--- a/chrome/browser/webview/webview_constants.cc
+++ b/chrome/browser/webview/webview_constants.cc
@@ -6,6 +6,13 @@
 
 namespace webview_constants {
 
+// Events.
+const char kEventLoadCommit[] = "webview.onLoadCommit";
+
+// Parameters/properties on events.
+const char kIsTopLevel[] = "isTopLevel";
+const char kUrl[] = "url";
+
 // Attributes.
 const char kAttributeApi[] = "api";