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, 4 insertions, 12 deletions

diff --git a/src/codec/SkCodec_wbmp.cpp b/src/codec/SkCodec_wbmp.cpp
index 86dce5cc89..52535e1f02 100644
--- a/src/codec/SkCodec_wbmp.cpp
+++ b/src/codec/SkCodec_wbmp.cpp
@@ -66,16 +66,8 @@ static bool read_header(SkStream* stream, SkISize* size) {
     return true;
 }
 
-bool SkWbmpCodec::handleRewind() {
-    SkCodec::RewindState rewindState = this->rewindIfNeeded();
-    if (rewindState == kCouldNotRewind_RewindState) {
-        return false;
-    } else if (rewindState == kRewound_RewindState) {
-        if (!read_header(this->stream(), NULL)) {
-            return false;
-        }
-    }
-    return true;
+bool SkWbmpCodec::onRewind() {
+    return read_header(this->stream(), NULL);
 }
 
 SkSwizzler* SkWbmpCodec::initializeSwizzler(const SkImageInfo& info,
@@ -117,7 +109,7 @@ SkCodec::Result SkWbmpCodec::onGetPixels(const SkImageInfo& info,
                                          const Options& options,
                                          SkPMColor ctable[],
                                          int* ctableCount) {
-    if (!this->handleRewind()) {
+    if (!this->rewindIfNeeded()) {
         return kCouldNotRewind;
     }
     if (options.fSubset) {
@@ -197,7 +189,7 @@ public:
     SkCodec::Result onStart(const SkImageInfo& dstInfo,
             const SkCodec::Options& options, SkPMColor inputColorTable[],
             int* inputColorCount) {
-        if (!fCodec->handleRewind()) {
+        if (!fCodec->rewindIfNeeded()) {
             return SkCodec::kCouldNotRewind;
         }
         if (options.fSubset) {