Timeline: fix a bunch of references to out-of-file privates

third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js

Index: third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js b/third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js
index 143b83fc2e77f0b072fee92377fa194a840243ad..9daeb842bb168367b5b9e388bef5391b89cbc328 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js
@@ -492,6 +492,21 @@ UI.TimelineOverviewBase = class extends UI.VBox {
     this._context = this._canvas.getContext('2d');
   }
 
+  /** @return {number} */
+  width() {
+    return this._canvas.width;
+  }
+
+  /** @return {number} */
+  height() {
+    return this._canvas.height;
+  }
+
+  /** @return {!CanvasRenderingContext2D} */
+  context() {
+    return this._context;
+  }
+
   /**
    * @override
    */