Tweak PDF getThumbnail message and related code

- Change PluginController.requestThumbnail() to take a page index.
  Adjust its 2 callers.
- Rename the getThumbnail message's "page" key to "pageIndex".

Change-Id: Ib9b52cc1f67dae332a624ee8575516be0142429e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5789329
Reviewed-by: Andy Phan <andyphan@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1343016}

chrome/browser/resources/pdf/controller.ts

@@ -330,11 +330,10 @@ export class PluginController implements ContentController {
    * Post a thumbnail request message to the plugin.
    * @return A promise holding the thumbnail response from the plugin.
    */
-  requestThumbnail(page: number): Promise<ThumbnailMessageData> {
+  requestThumbnail(pageIndex: number): Promise<ThumbnailMessageData> {
     return this.postMessageWithReply_({
       type: 'getThumbnail',
-      // The plugin references pages using zero-based indices.
-      page: page - 1,
+      pageIndex: pageIndex,
     });
   }
 

chrome/browser/resources/pdf/elements/viewer_thumbnail_bar.ts

@@ -95,7 +95,8 @@ export class ViewerThumbnailBarElement extends CrLitElement {
               return;
             }
 
-            this.pluginController_.requestThumbnail(thumbnail.pageNumber)
+            // Convert to zero-based page index.
+            this.pluginController_.requestThumbnail(thumbnail.pageNumber - 1)
                 .then(response => {
                   const array = new Uint8ClampedArray(response.imageData);
                   const imageData = new ImageData(array, response.width);

chrome/test/data/pdf/plugin_controller_test.ts

@@ -6,7 +6,7 @@ import {PluginController} from 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgieh
 
 const tests = [
   async function testRequestThumbnail() {
-    const data = await PluginController.getInstance().requestThumbnail(1);
+    const data = await PluginController.getInstance().requestThumbnail(0);
 
     const expectedWidth = 108 * window.devicePixelRatio;
     const expectedHeight = 140 * window.devicePixelRatio;

pdf/pdf_view_web_plugin.cc

@@ -1482,7 +1482,7 @@ void PdfViewWebPlugin::HandleGetSelectedTextMessage(
 
 void PdfViewWebPlugin::HandleGetThumbnailMessage(
     const base::Value::Dict& message) {
-  const int page_index = message.FindInt("page").value();
+  const int page_index = message.FindInt("pageIndex").value();
   base::Value::Dict reply = PrepareReplyMessage("getThumbnailReply", message);
 
   engine_->RequestThumbnail(