Switch tracing to new flexbox.

tracing/tracing/ui/extras/about_tracing/profiling_view.html

Index: tracing/tracing/ui/extras/about_tracing/profiling_view.html
diff --git a/tracing/tracing/ui/extras/about_tracing/profiling_view.html b/tracing/tracing/ui/extras/about_tracing/profiling_view.html
index a14d757b248b16ff2a65bb87849bec28095896a4..d1f6c93c3ff55decc47b047b678ed7ca3ee8fe92 100644
--- a/tracing/tracing/ui/extras/about_tracing/profiling_view.html
+++ b/tracing/tracing/ui/extras/about_tracing/profiling_view.html
@@ -22,8 +22,8 @@ found in the LICENSE file.
 
 <style>
 x-profiling-view {
-  -webkit-flex-direction: column;
-  display: -webkit-flex;
+  flex-direction: column;
+  display: flex;
   padding: 0;
 }
 
@@ -32,7 +32,7 @@ x-profiling-view .controls #save-button {
 }
 
 x-profiling-view > tr-ui-timeline-view {
-  -webkit-flex: 1 1 auto;
+  flex: 1 1 auto;
   min-height: 0;
 }