Allow SkLazyPixelRef to use SkScaledImageCache

-   SkScaledImageCache:
    -   Add new FindAndLock/AddAndLock variants that work well with
        SkLazyPixelRefs (take width, height, generation_id).
    -   Add static versions of these new variants.

-   SkLazyPixelRef:
    -   If NULL passed in as SkImageCache* in the constructor, it will
        now default to using the static SkScaledImageCache methods to
        cache decoded images.
    -   If (fImageCache==NULL), the default allocator can be changed
        with the setAllocator method.  If (fImageCache!=NULL), the
        SkImageCache handles allocation.

-   CachedDecodingPixelRefTest to test the new functionality.

BUG=
R=scroggo@google.com, mtklein@google.com, reed@google.com

Author: halcanary@google.com

Review URL: https://codereview.chromium.org/37343002

git-svn-id: http://skia.googlecode.com/svn/trunk/src@12006 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed