[turbolizer] Use fewer event handlers

Instead of attaching an event handler to every line in the code view,
attach it only to the container and find the lineNumber based on the event
target element.

Notry: true
Change-Id: I1920f7a200cf2f5ffaf259c0aaa04d6fb6698d2d
Bug: v8:7327
Reviewed-on: https://chromium-review.googlesource.com/c/1346110
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57670}

tools/turbolizer/src/code-view.ts

@@ -182,8 +182,16 @@ export class CodeView extends View {
         console.log(e);
       }
 
-      view.divNode.onclick = function (e) {
-        view.selectionHandler.clear();
+      view.divNode.onclick = function (e: MouseEvent) {
+        if (e.target instanceof Element && e.target.tagName == "DIV") {
+          const targetDiv = e.target as HTMLDivElement;
+          if (targetDiv.classList.contains("line-number")) {
+            e.stopPropagation();
+            view.onSelectLine(Number(targetDiv.dataset.lineNumber), !e.shiftKey);
+          }
+        } else {
+          view.selectionHandler.clear();
+        }
       }
 
       const base: number = source.startPosition;
@@ -256,10 +264,6 @@ export class CodeView extends View {
     lineNumberElement.classList.add("line-number");
     lineNumberElement.dataset.lineNumber = lineNumber;
     lineNumberElement.innerText = lineNumber;
-    lineNumberElement.onclick = function (e) {
-      e.stopPropagation();
-      view.onSelectLine(lineNumber, !e.shiftKey);
-    }
     lineElement.insertBefore(lineNumberElement, lineElement.firstChild)
     // Don't add lines to source positions of not in backwardsCompatibility mode.
     if (this.source.backwardsCompatibility === true) {