DM: make GPU tasks multithreaded again. Big refactor.

dm/DMTaskRunner.cpp

 #include "DMTaskRunner.h"
 #include "DMTask.h"
 
 namespace DM {
 
+TaskRunner::TaskRunner(int cpuThreads, int gpuThreads) : fCpu(cpuThreads), fGpu(gpuThreads) {}
 
-TaskRunner::TaskRunner(int cputhreads)
-    : fMain(cputhreads)
-    , fGpu(1) {
-    // Enqueue a task on the GPU thread to create a GrContextFactory.
-    struct Create : public SkRunnable {
-        Create(GrContextFactory** ptr) : fPtr(ptr) {}
-        void run() SK_OVERRIDE {
-            *fPtr = SkNEW(GrContextFactory);
-            delete this;
-        }
-        GrContextFactory** fPtr;
-    };
-    fGpu.add(SkNEW_ARGS(Create, (&fGrContextFactory)));
-}
+void TaskRunner::add(CpuTask* task) { fCpu.add(task); }
 
-void TaskRunner::add(Task* task) {
-    if (task->usesGpu()) {
-        fGpu.add(task);
-    } else {
-        fMain.add(task);
-    }
-}
+void TaskRunner::add(GpuTask* task) { fGpu.add(task); }
 
 void TaskRunner::wait() {
-    // Enqueue a task on the GPU thread to destroy the GrContextFactory.
-    struct Delete : public SkRunnable {
-        Delete(GrContextFactory* ptr) : fPtr(ptr) {}
-        void run() SK_OVERRIDE {
-            delete fPtr;
-            delete this;
-        }
-        GrContextFactory* fPtr;
-    };
-    fGpu.add(SkNEW_ARGS(Delete, (fGrContextFactory)));
-
-    // These wait calls block until the threadpool is done.  We don't allow
-    // children to spawn new GPU tasks so we can wait for that first knowing
-    // we'll never try to add to it later.  Same can't be said of fMain: fGpu
-    // and fMain can both add tasks to fMain, so we have to wait for that last.
+    // These wait calls block until each threadpool is done.  We don't allow
+    // spawning new child GPU tasks, so we can wait for that first knowing
+    // we'll never try to add to it later.  Same can't be said of the CPU pool:
+    // both CPU and GPU tasks can spawn off new CPU work, so we wait for that last.
     fGpu.wait();
-    fMain.wait();
+    fCpu.wait();
 }
 
 }  // namespace DM