Make DM play nice with the plan to split CPU and GPU work.

dm/DMTask.cpp

 #include "DMTask.h"
 #include "DMTaskRunner.h"
+#include "SkCommandLineFlags.h"
+
+DEFINE_bool(cpu, true, "Master switch for running CPU-bound work.");
+DEFINE_bool(gpu, true, "Master switch for running GPU-bound work.");
 
 namespace DM {
 
 Task::Task(Reporter* reporter, TaskRunner* taskRunner)
     : fReporter(reporter)
     , fTaskRunner(taskRunner)
     , fDepth(0) {
     fReporter->start();
 }
 
@@ skipping 22 matching lines @@
 
 void Task::spawnChild(CpuTask* task) {
     fTaskRunner->add(task);
 }
 
 CpuTask::CpuTask(Reporter* reporter, TaskRunner* taskRunner) : Task(reporter, taskRunner) {}
 CpuTask::CpuTask(const Task& parent) : Task(parent) {}
 
 void CpuTask::run() {
     this->start();
-    if (!this->shouldSkip()) {
+    if (FLAGS_cpu && !this->shouldSkip()) {
         this->draw();
     }
     this->finish();
     SkDELETE(this);
 }
 
 GpuTask::GpuTask(Reporter* reporter, TaskRunner* taskRunner) : Task(reporter, taskRunner) {}
 
 void GpuTask::run(GrContextFactory& factory) {
     this->start();
-    if (!this->shouldSkip()) {
+    if (FLAGS_gpu && !this->shouldSkip()) {
         this->draw(&factory);
     }
     this->finish();
     SkDELETE(this);
 }
 
 
 
 }  // namespace DM