Diagnostics: Fix CPU chart overflow issue

Bug: 1125150
Test: browser_tests --gtest_filter=DiagnosticsApp*
Change-Id: I78c14f59c1df348c5a9cf246346122877c7aeb7b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2604976Reviewed-by: Joon Ahn <joonbug@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Commit-Queue: Michael Checo <michaelcheco@google.com>
Cr-Commit-Position: refs/heads/master@{#842747}

chromeos/components/diagnostics_ui/resources/realtime_cpu_chart.js

@@ -152,7 +152,7 @@ Polymer({
   ready() {
     this.setScaling_();
     this.initializeChart_();
-    window.addEventListener('resize', (e) => this.updateChartWidth_());
+    window.addEventListener('resize', () => this.updateChartWidth_());
 
     // Set the initial chart width.
     this.updateChartWidth_();
@@ -208,19 +208,10 @@ Polymer({
         d3.scaleLinear().domain([0, this.numDataPoints_ - 2]).range([
           0, this.graphWidth_
         ]);
-  },
-
-  /** @private */
-  initializeChart_() {
-    const chartGroup = d3.select(this.$$('#chartGroup'));
-
-    // Position chartGroup inside the margin.
-    chartGroup.attr(
-        'transform',
-        'translate(' + this.padding_.left + ',' + this.padding_.top + ')');
 
     // Draw the y-axis legend and also draw the horizontal gridlines by
     // reversing the ticks back into the chart body.
+    const chartGroup = d3.select(this.$$('#chartGroup'));
     chartGroup.select('#gridLines')
         .call(
             d3.axisLeft(/** @type {!d3.LinearScale} */ (this.yAxisScaleFn_))
@@ -230,6 +221,16 @@ Polymer({
                 .tickSize(-this.graphWidth_)  // Extend the ticks into the
                                               // entire graph as gridlines.
         );
+  },
+
+  /** @private */
+  initializeChart_() {
+    const chartGroup = d3.select(this.$$('#chartGroup'));
+
+    // Position chartGroup inside the margin.
+    chartGroup.attr(
+        'transform',
+        'translate(' + this.padding_.left + ',' + this.padding_.top + ')');
 
     const plotGroup = d3.select(this.$$('#plotGroup'));