[Devtools] Fix minor flexbox filmstrip regression

Fixes a scaling regression when console drawer is shrinking and
timeline overlays filmstrip.

R=alph
BUG=739143

Change-Id: Ice042964ed85d0cfad0ce59b67d982b04594217e
Reviewed-on: https://chromium-review.googlesource.com/562038
Commit-Queue: Blaise Bruer <allada@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484986}

third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js

@@ -52,7 +52,7 @@ Network.NetworkPanel = class extends UI.Panel {
     this._filterBar.show(this.element);
     this.setDefaultFocusedChild(this._filterBar);
 
-    this._filmStripPlaceholderElement = this.element.createChild('div');
+    this._filmStripPlaceholderElement = this.element.createChild('div', 'network-film-strip-placeholder');
 
     // Create top overview component.
     this._overviewPane = new PerfUI.TimelineOverviewPane('network');

third_party/WebKit/Source/devtools/front_end/network/networkPanel.css

@@ -120,6 +120,10 @@
     flex: none !important;
 }
 
+.network-film-strip-placeholder {
+    flex-shrink: 0;
+}
+
 .network-blocked-urls {
     border-top: 1px solid #dadada;
     flex: 104px 0 0;