Consolidate SkCodec functions for handling rewind

Previously, many of our codec implementations followed the same
pattern (often in a function named handleRewind):

switch (this->rewindIfNeeded()) {
  case CouldNotRewind:
    return CouldNotRewind;
  case NoRewindNecessary:
    // keep going
    break;
  case Rewound:
     <re-read header etc>
    break;
}

In this CL, remove the enum, and put the piece that happens in the
Rewound case into a virtual function, onRewind. rewindIfNeeded now
contains the common pieces from various functions named handleRewind.

In SkBmpCodec, add a function that returns whether the BMP is in ICO,
so it can have a common implementation for onRewind.

BUG=skia:3257

Review URL: https://codereview.chromium.org/1288483002

1 files changed, 10 insertions, 2 deletions

diff --git a/src/codec/SkBmpCodec.h b/src/codec/SkBmpCodec.h
index 51d0300091..71006f7315 100644
--- a/src/codec/SkBmpCodec.h
+++ b/src/codec/SkBmpCodec.h
@@ -63,10 +63,18 @@ protected:
      */
     static bool ReadHeader(SkStream*, bool inIco, SkCodec** codecOut);
 
+    bool onRewind() override;
+
     /*
-     * Rewinds the image stream if necessary
+     * Returns whether this BMP is part of an ICO image.
      */
-    bool handleRewind(bool inIco);
+    bool inIco() const {
+        return this->onInIco();
+    }
+
+    virtual bool onInIco() const {
+        return false;
+    }
 
     /*
      * Get the destination row to start filling from