[turbolizer] Fix selection bugs and performance problems

tools/turbolizer/disassembly-view.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 "use strict";
 
 class DisassemblyView extends TextView {
   constructor(id, broker, sortedPositionList) {
     super(id, broker, null, false);
-    this.pos_start = -1;
-    this.pos_lines = null;
-    this.addr_event_counts = null;
-    this.total_event_counts = null;
 
     let view = this;
     let ADDRESS_STYLE = {
       css: 'tag',
       location: function(text) {
         ADDRESS_STYLE.last_address = text;
         return undefined;
       }
     };
     let ADDRESS_LINK_STYLE = {
@@ skipping 122 matching lines @@
     return result;
   }
 
   initializeContent(data, rememberedSelection) {
     this.data = data;
     super.initializeContent(data, rememberedSelection);
   }
 
   initializeCode(sourceText, sourcePosition) {
     let view = this;
+    view.pos_start = -1;
+    view.addr_event_counts = null;
+    view.total_event_counts = null;
     view.pos_lines = new Array();
     // Comment lines for line 0 include sourcePosition already, only need to
     // add sourcePosition for lines > 0.
     view.pos_lines[0] = sourcePosition;
     if (sourceText != "") {
       let base = sourcePosition;
       let current = 0;
       let source_lines = sourceText.split("\n");
       for (let i = 1; i < source_lines.length; i++) {
         // Add 1 for newline character that is split off.
@@ skipping 64 matching lines @@
           // Pad extra spaces to keep alignment for all instructions.
           str = (" ".repeat(10) + str).slice(-10);
 
           fragments.splice(0, 0, view.createFragment(str, css_cls));
         }
       }
     }
     return fragments;
   }
 }