DM: make GPU tasks multithreaded again. Big refactor.

dm/DMWriteTask.cpp

 #include "DMWriteTask.h"
 
 #include "DMUtil.h"
 #include "SkColorPriv.h"
 #include "SkCommandLineFlags.h"
 #include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkString.h"
 #include "SkUnPreMultiply.h"
 
 DEFINE_string2(writePath, w, "", "If set, write GMs here as .pngs.");
 
 namespace DM {
 
 // Splits off the last N suffixes of name (splitting on _) and appends them to out.
 // Returns the total number of characters consumed.
 static int split_suffixes(int N, const char* name, SkTArray<SkString>* out) {
     SkTArray<SkString> split;
     SkStrSplit(name, "_", &split);
     int consumed = 0;
     for (int i = 0; i < N; i++) {
         // We're splitting off suffixes from the back to front.
         out->push_back(split[split.count()-i-1]);
         consumed += out->back().size() + 1;  // Add one for the _.
     }
     return consumed;
 }
 
-WriteTask::WriteTask(const Task& parent, SkBitmap bitmap) : Task(parent), fBitmap(bitmap) {
+WriteTask::WriteTask(const Task& parent, SkBitmap bitmap) : CpuTask(parent), fBitmap(bitmap) {
     const int suffixes = parent.depth() + 1;
     const SkString& name = parent.name();
     const int totalSuffixLength = split_suffixes(suffixes, name.c_str(), &fSuffixes);
     fGmName.set(name.c_str(), name.size()-totalSuffixLength);
 }
 
 void WriteTask::makeDirOrFail(SkString dir) {
     if (!sk_mkdir(dir.c_str())) {
         this->fail();
     }
@@ skipping 105 matching lines @@
         for (size_t i = 0; i < bitmap.getSize()/4; i++) {
             dst[i] = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(src[i]);
         }
         bitmap.swap(unpremul);
     }
 
     return BitmapsEqual(expected, bitmap);
 }
 
 }  // namespace DM