Make image_decoder a Leaky LazyInstance

chrome/browser/bitmap_fetcher/bitmap_fetcher.h

Index: chrome/browser/bitmap_fetcher/bitmap_fetcher.h
diff --git a/chrome/browser/bitmap_fetcher/bitmap_fetcher.h b/chrome/browser/bitmap_fetcher/bitmap_fetcher.h
index ac26bbf6d36d4a9d0c5c79bb8cbd00b3699acfdb..f15be00a028971be75f5a0f9ef766aa9aff6255a 100644
--- a/chrome/browser/bitmap_fetcher/bitmap_fetcher.h
+++ b/chrome/browser/bitmap_fetcher/bitmap_fetcher.h
@@ -21,7 +21,10 @@ class URLRequestContextGetter;
 namespace chrome {
 
 // Asynchrounously fetches an image from the given URL and returns the
-// decoded Bitmap to the provided BitmapFetcherDelegate.
+// decoded Bitmap to the provided BitmapFetcherDelegate. This class is
+// deprecated and will be removed once crbug.com/<TODO(twellington): fill
+// this in once deprecation is approved and bug is created> is resolved. Use
+// BitmapBatchFetcher instead.

[Nico, 2015/02/18 20:59:17]

To me, it seems like a better strategy to me to swap out the implementation of
this class transparently instead of changing all clients to use the new class –
they should be mostly interface-compatible right? That's what abstractions are
for, after all.

Maybe the implementation could pick one of the two behaviors based on a flag,
then you can roll this out behind a flag and don't need a new class at all – and
once you're happy with how the flag performs, you can turn it on by default and
rip out the old code.

 class BitmapFetcher : public net::URLFetcherDelegate,
                       public ImageDecoder::Delegate {
  public: