Switch tracing to new flexbox.

tracing/tracing/ui/extras/about_tracing/record_selection_dialog.html

Index: tracing/tracing/ui/extras/about_tracing/record_selection_dialog.html
diff --git a/tracing/tracing/ui/extras/about_tracing/record_selection_dialog.html b/tracing/tracing/ui/extras/about_tracing/record_selection_dialog.html
index 8eb9399f420e49fcfbacff91b806b14a794911d9..70c591779bbc8388a7f730ad6223d97e7a7ba81f 100644
--- a/tracing/tracing/ui/extras/about_tracing/record_selection_dialog.html
+++ b/tracing/tracing/ui/extras/about_tracing/record_selection_dialog.html
@@ -13,8 +13,8 @@ found in the LICENSE file.
 <template id="record-selection-dialog-template">
   <style>
   .categories-column-view {
-    display: -webkit-flex;
-    -webkit-flex-direction: column;
+    display: flex;
+    flex-direction: column;
     font-family: sans-serif;
     max-width: 640px;
     min-height: 0;
@@ -33,8 +33,8 @@ found in the LICENSE file.
   }
 
   .categories-selection {
-    display: -webkit-flex;
-    -webkit-flex-direction: row;
+    display: flex;
+    flex-direction: row;
   }
 
   .category-presets {
@@ -60,9 +60,9 @@ found in the LICENSE file.
 
   .default-enabled-categories,
   .default-disabled-categories {
-    -webkit-flex: 1 1 auto;
-    display: -webkit-flex;
-    -webkit-flex-direction: column;
+    flex: 1 1 auto;
+    display: flex;
+    flex-direction: column;
     padding: 4px;
     width: 300px;
   }
@@ -73,9 +73,9 @@ found in the LICENSE file.
   }
 
   .tracing-modes {
-    -webkit-flex: 1 0 auto;
-    display: -webkit-flex;
-    -webkit-flex-direction: reverse;
+    flex: 1 0 auto;
+    display: flex;
+    flex-direction: reverse;
     padding: 4px;
     border-bottom: 2px solid #ddd;
     border-top: 2px solid #ddd;
@@ -99,14 +99,14 @@ found in the LICENSE file.
   .categories {
     font-size: 80%;
     padding: 10px;
-    -webkit-flex: 1 1 auto;
+    flex: 1 1 auto;
   }
 
   .group-selectors {
     font-size: 80%;
     border-bottom: 1px solid #ddd;
     padding-bottom: 6px;
-    -webkit-flex: 0 0 auto;
+    flex: 0 0 auto;
   }
 
   .group-selectors button {
@@ -114,9 +114,9 @@ found in the LICENSE file.
   }
 
   .record-selection-dialog .labeled-option-group {
-    -webkit-flex: 0 0 auto;
-    -webkit-flex-direction: column;
-    display: -webkit-flex;
+    flex: 0 0 auto;
+    flex-direction: column;
+    display: flex;
   }
 
   .record-selection-dialog .labeled-option {