content: Implement dynamic priorities for raster threads.

base/threading/simple_thread.cc

Index: base/threading/simple_thread.cc
diff --git a/base/threading/simple_thread.cc b/base/threading/simple_thread.cc
index 7059ceab76661428a3a4e9f7eb124e524b162ebe..3e8ff97853657bb7859ca2f2b9522ded0aeb6dce 100644
--- a/base/threading/simple_thread.cc
+++ b/base/threading/simple_thread.cc
@@ -12,15 +12,24 @@
 namespace base {
 
 SimpleThread::SimpleThread(const std::string& name_prefix)
-    : name_prefix_(name_prefix), name_(name_prefix),
-      thread_(), event_(true, false), tid_(0), joined_(false) {
-}
+    : name_prefix_(name_prefix),
+      name_(name_prefix),
+      thread_(),
+      event_(true, false),
+      tid_(0),
+      joined_(false),
+      priority_(options_.priority()) {}
 
 SimpleThread::SimpleThread(const std::string& name_prefix,
                            const Options& options)
-    : name_prefix_(name_prefix), name_(name_prefix), options_(options),
-      thread_(), event_(true, false), tid_(0), joined_(false) {
-}
+    : name_prefix_(name_prefix),
+      name_(name_prefix),
+      options_(options),
+      thread_(),
+      event_(true, false),
+      tid_(0),
+      joined_(false),
+      priority_(options_.priority()) {}
 
 SimpleThread::~SimpleThread() {
   DCHECK(HasBeenStarted()) << "SimpleThread was never started.";
@@ -66,6 +75,63 @@ void SimpleThread::ThreadMain() {
   Run();
 }
 
+bool SimpleThread::SetThreadPriority(ThreadPriority priority) {
+  DCHECK(HasBeenStarted())
+      << "Tried to set a priority of never-started thread.";
+
+  if (PlatformThread::SetChildThreadPriorityInCurrentProcess(thread_, tid_,
+                                                             priority)) {
+    priority_ = priority;
+    return true;
+  }
+  return false;
+}
+
+// Must have default priority either equal to higher or lower priority.
+DynamicPriorityThread::DynamicPriorityThread(const PrioritySet& priorities,
+                                             const std::string& name_prefix,
+                                             const Options& options)
+    : SimpleThread(name_prefix, options),
+      priorities_(priorities),
+      dynamic_priorities_(false),
+      priority_changed_(false) {
+  CHECK(priorities_.higher_priority == priorities_.default_priority ||
+        priorities_.lower_priority == priorities_.default_priority);
+  dynamic_priorities_ =
+      priorities_.higher_priority != priorities_.lower_priority;
+}
+
+bool DynamicPriorityThread::Speedup() {
+  if (dynamic_priorities_ &&
+      (GetThreadPriority() != priorities_.higher_priority)) {
+    SetThreadPriority(priorities_.higher_priority);
+    priority_changed_ = true;
+    return true;
+  }
+  return false;
+}
+
+bool DynamicPriorityThread::Slowdown() {
+  if (dynamic_priorities_ &&
+      (GetThreadPriority() != priorities_.lower_priority)) {
+    SetThreadPriority(priorities_.lower_priority);
+    priority_changed_ = true;
+    return true;
+  }
+  return false;
+}
+
+bool DynamicPriorityThread::RestoreDefaultPriority() {
+  if (dynamic_priorities_ && priority_changed_) {
+    priority_changed_ = false;
+    SetThreadPriority(priorities_.default_priority);
+    // LOG(ERROR) << "\nPRAS:: [" << std::hex << this << "] "
+    //            << GetPrioritySetForDebugging() << ".  Restored to default.";
+    return true;
+  }
+  return false;
+}
+
 DelegateSimpleThread::DelegateSimpleThread(Delegate* delegate,
                                            const std::string& name_prefix)
     : SimpleThread(name_prefix),