Add general-purpose vlogs for ax_image_annotator.

This is enough to quickly check how many images it's trying to label
and what successes we got back. To use, run Chrome with:

--enable-logging=stderr --vmodule="*ax_image_annotator*=1"

Bug: 905419
Change-Id: If3ceedbbb1a4d673f2045319836046690ccf7ed9
Reviewed-on: https://chromium-review.googlesource.com/c/1493198
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636730}

content/renderer/accessibility/ax_image_annotator.cc

@@ -15,6 +15,7 @@
 #include "third_party/blink/public/web/web_ax_object.h"
 #include "third_party/blink/public/web/web_document.h"
 #include "third_party/blink/public/web/web_element.h"
+#include "third_party/blink/public/web/web_local_frame.h"
 #include "third_party/blink/public/web/web_node.h"
 #include "ui/gfx/geometry/size.h"
 #include "url/gurl.h"
@@ -73,6 +74,8 @@ void AXImageAnnotator::OnImageAdded(blink::WebAXObject& image) {
       image_id, image_info.GetImageProcessor(),
       base::BindOnce(&AXImageAnnotator::OnImageAnnotated,
                      weak_factory_.GetWeakPtr(), image));
+  VLOG(1) << "Requesting annotation for " << image_id << " from page "
+          << GetDocumentUrl();
 }
 
 void AXImageAnnotator::OnImageUpdated(blink::WebAXObject& image) {
@@ -164,6 +167,8 @@ SkBitmap AXImageAnnotator::GetImageData(const blink::WebAXObject& image) {
   if (node.IsNull() || !node.IsElementNode())
     return SkBitmap();
   blink::WebElement element = node.To<blink::WebElement>();
+  VLOG(1) << "Uploading pixels for " << element.ImageContents().width() << " x "
+          << element.ImageContents().height() << " image";
   return element.ImageContents();
 }
 
@@ -217,6 +222,15 @@ void AXImageAnnotator::OnImageAnnotated(
       base::JoinString(contextualized_strings, base::ASCIIToUTF16(". ")));
   image_annotations_.at(image.AxID()).set_annotation(contextualized_string);
   render_accessibility_->MarkWebAXObjectDirty(image, false /* subtree */);
+
+  VLOG(1) << "Annotating image on page " << GetDocumentUrl() << " - "
+          << contextualized_string;
+}
+
+std::string AXImageAnnotator::GetDocumentUrl() const {
+  const blink::WebLocalFrame* frame =
+      render_accessibility_->render_frame()->GetWebFrame();
+  return frame->GetDocument().Url().GetString().Utf8();
 }
 
 }  // namespace content

content/renderer/accessibility/ax_image_annotator.h

@@ -83,6 +83,9 @@ class AXImageAnnotator final : public base::CheckedObserver {
   void OnImageAnnotated(const blink::WebAXObject& image,
                         image_annotation::mojom::AnnotateImageResultPtr result);
 
+  // Only for local logging when running with --v=1.
+  std::string GetDocumentUrl() const;
+
   // Weak, owns us.
   RenderAccessibilityImpl* const render_accessibility_;