Unprefix flexbox properties in various CSS files

Source/core/inspector/InspectorOverlayPage.html

Index: Source/core/inspector/InspectorOverlayPage.html
diff --git a/Source/core/inspector/InspectorOverlayPage.html b/Source/core/inspector/InspectorOverlayPage.html
index a41e3f7bc49c6d8b8be863eb56ab9307bdd68a85..fc150af8731779868c399fb46b1a6c814808a808 100644
--- a/Source/core/inspector/InspectorOverlayPage.html
+++ b/Source/core/inspector/InspectorOverlayPage.html
@@ -70,15 +70,15 @@ body.platform-linux {
 }
 
 .controls-line {
-    display: -webkit-flex;
-    -webkit-justify-content: center;
+    display: flex;
+    justify-content: center;
     margin: 10px 0;
 }
 
 .message-box {
     padding: 2px 4px;
-    display: -webkit-flex;
-    -webkit-align-items: center;
+    display: flex;
+    align-items: center;
     cursor: default;
 }