arc: Support non-standard display scale factors.

chrome/browser/ui/app_list/arc/arc_app_icon.cc

Index: chrome/browser/ui/app_list/arc/arc_app_icon.cc
diff --git a/chrome/browser/ui/app_list/arc/arc_app_icon.cc b/chrome/browser/ui/app_list/arc/arc_app_icon.cc
index 8c9c2c97e7ebef6200b0d8f0c3cd835abf44906f..52474879652556a99855eb35222eee733e9c519a 100644
--- a/chrome/browser/ui/app_list/arc/arc_app_icon.cc
+++ b/chrome/browser/ui/app_list/arc/arc_app_icon.cc
@@ -213,11 +213,7 @@ void ArcAppIcon::DecodeRequest::OnImageDecoded(const SkBitmap& bitmap) {
     return;
   }
 
-  gfx::ImageSkia image_skia;
-  image_skia.AddRepresentation(gfx::ImageSkiaRep(
-      bitmap,
-      ui::GetScaleForScaleFactor(scale_factor_)));
-  host_->Update(&image_skia);
+  host_->Update(scale_factor_, bitmap);
   host_->DiscardDecodeRequest(this);
 }
 
@@ -359,18 +355,32 @@ void ArcAppIcon::OnIconRead(
   }
 }
 
-void ArcAppIcon::Update(const gfx::ImageSkia* image) {
+void ArcAppIcon::Update(ui::ScaleFactor scale_factor, const SkBitmap& bitmap) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  CHECK(image && !image->isNull());
 
-  std::vector<gfx::ImageSkiaRep> reps = image->image_reps();
-  for (const auto& image_rep : reps) {
-    if (ui::IsSupportedScale(image_rep.scale())) {
-      image_skia_.RemoveRepresentation(image_rep.scale());
-      image_skia_.AddRepresentation(image_rep);

[oshima, 2017/05/26 18:13:23]

I looked into a bit more, and the problem seems to be that it has a cache
created from default app icon.
You can clear the cache for unsupported scales like this:

  for (const gfx::ImageSkiaRep& image_rep_to_test : image_skia_.image_reps()) {
    if (!ui::IsSupportedScale(image_rep_to_test.scale()))
      image_skia_.RemoveRepresentation(image_rep_to_test.scale());
  }

I tested on caroline + 1.25dsf and this did fix  both issues.

Maybe ImageSkia should have a method to clear the cache for unsupported scales,
so you can add it to ImageSkia.
I'm fine with either way.

[khmel, 2017/05/26 19:31:20]

Thanks for offline chat! As discussed I moved invalidation code to ImageSkia.

PTAL

+  gfx::ImageSkiaRep image_rep(bitmap, ui::GetScaleForScaleFactor(scale_factor));
+  DCHECK(ui::IsSupportedScale(image_rep.scale()));
+
+  image_skia_.RemoveRepresentation(image_rep.scale());
+
+  // Regenerate existing non-supported image representations that depend on the
+  // rep of |scale_factor|.
+  std::vector<float> scales_to_regenerate;
+  for (const gfx::ImageSkiaRep& image_rep_to_test : image_skia_.image_reps()) {
+    if (gfx::ImageSkia::MapToSupportedScale(image_rep_to_test.scale()) ==
+        image_rep.scale()) {
+      DCHECK(!ui::IsSupportedScale(image_rep_to_test.scale()));
+      scales_to_regenerate.push_back(image_rep_to_test.scale());
     }
   }
 
+  image_skia_.AddRepresentation(image_rep);
+
+  for (float scale_to_regenerate : scales_to_regenerate) {
+    image_skia_.RemoveRepresentation(scale_to_regenerate);
+    image_skia_.GetRepresentation(scale_to_regenerate);
+  }
+
   observer_->OnIconUpdated(this);
 }