Add full SetThreadPriority support to Windows.

base/threading/platform_thread_unittest.cc

Index: base/threading/platform_thread_unittest.cc
diff --git a/base/threading/platform_thread_unittest.cc b/base/threading/platform_thread_unittest.cc
index 21260e5ec36bd27dcdc9bf1500167e32fbab2524..0a4dcb95002cc9c4c83b78a0c02a415e5137236d 100644
--- a/base/threading/platform_thread_unittest.cc
+++ b/base/threading/platform_thread_unittest.cc
@@ -3,10 +3,14 @@
 // found in the LICENSE file.
 
 #include "base/compiler_specific.h"
+#include "base/macros.h"
 #include "base/threading/platform_thread.h"
-
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
 namespace base {
 
 // Trivial tests that thread runs and doesn't crash on create and join ---------
@@ -116,4 +120,121 @@ TEST(PlatformThreadTest, FunctionTimesTen) {
   EXPECT_EQ(main_thread_id, PlatformThread::CurrentId());
 }
 
+namespace {
+
+const ThreadPriority kThreadPriorityTestValues[] = {
+// Disable non-normal priority toggling on POSIX as it appears to be broken
+// (http://crbug.com/468793). This is prefered to disabling the tests altogether
+// on POSIX as it at least provides coverage for running this code under
+// "normal" priority.
+#if !defined(OS_POSIX)
+    kThreadPriority_RealtimeAudio,
+    kThreadPriority_Display,
+    kThreadPriority_Background,
+#endif  // !defined(OS_POSIX)
+    // Keep normal last to test unbackgrounding.
+    kThreadPriority_Normal
+};
+
+}  // namespace
+
+// Test changing another thread's priority.
+// NOTE: This test is partially disabled on POSIX, see note above and
+// http://crbug.com/468793.
+TEST(PlatformThreadTest, ThreadPriorityOtherThread) {
+  PlatformThreadHandle current_handle(PlatformThread::CurrentHandle());
+
+  // Confirm that the current thread's priority is as expected.
+  EXPECT_EQ(kThreadPriority_Normal,
+            PlatformThread::GetThreadPriority(current_handle));
+
+  // Create a test thread.
+  FunctionTestThread thread;
+  PlatformThreadHandle handle;
+  ASSERT_TRUE(PlatformThread::Create(0, &thread, &handle));
+  EXPECT_NE(thread.thread_id(), PlatformThread::CurrentId());
+
+  // New threads should get normal priority by default.
+  EXPECT_EQ(kThreadPriority_Normal, PlatformThread::GetThreadPriority(handle));
+
+  // Toggle each supported priority on the test thread and confirm it only
+  // affects it (and not the current thread).
+  for (size_t i = 0; i < arraysize(kThreadPriorityTestValues); ++i) {
+    SCOPED_TRACE(i);
+
+    // Alter and verify the test thread's priority.
+    PlatformThread::SetThreadPriority(handle, kThreadPriorityTestValues[i]);
+    EXPECT_EQ(kThreadPriorityTestValues[i],
+              PlatformThread::GetThreadPriority(handle));
+
+    // Make sure the current thread was otherwise unaffected.
+    EXPECT_EQ(kThreadPriority_Normal,
+              PlatformThread::GetThreadPriority(current_handle));
+  }
+}
+
+// Test changing the current thread's priority (which has different semantics on
+// some platforms).
+// NOTE: This test is partially disabled on POSIX, see note above and
+// http://crbug.com/468793.
+TEST(PlatformThreadTest, ThreadPriorityCurrentThread) {
+  PlatformThreadHandle current_handle(PlatformThread::CurrentHandle());
+
+  // Confirm that the current thread's priority is as expected.
+  EXPECT_EQ(kThreadPriority_Normal,
+            PlatformThread::GetThreadPriority(current_handle));
+
+  // Create a test thread for verification purposes only.
+  FunctionTestThread thread;
+  PlatformThreadHandle handle;
+  ASSERT_TRUE(PlatformThread::Create(0, &thread, &handle));
+  EXPECT_NE(thread.thread_id(), PlatformThread::CurrentId());
+
+  // Confirm that the new thread's priority is as expected.
+  EXPECT_EQ(kThreadPriority_Normal, PlatformThread::GetThreadPriority(handle));
+
+  // Toggle each supported priority on the test thread and confirm it only
+  // affects it (and not the current thread).
+  for (size_t i = 0; i < arraysize(kThreadPriorityTestValues); ++i) {
+    SCOPED_TRACE(i);
+
+    // Alter and verify the current thread's priority.
+    PlatformThread::SetThreadPriority(current_handle,
+                                      kThreadPriorityTestValues[i]);
+    EXPECT_EQ(kThreadPriorityTestValues[i],
+              PlatformThread::GetThreadPriority(current_handle));
+
+    // Make sure the test thread was otherwise unaffected.
+    EXPECT_EQ(kThreadPriority_Normal,
+              PlatformThread::GetThreadPriority(handle));
+  }
+
+  // Restore current thread priority for follow-up tests.
+  PlatformThread::SetThreadPriority(current_handle, kThreadPriority_Normal);
+}
+
+#if defined(OS_WIN)
+// Explicitly test Windows' advanced background mode from current thread.
+TEST(PlatformThreadTest, BackgroundModeCurrentThread) {
+  PlatformThreadHandle current_handle(PlatformThread::CurrentHandle());
+
+  // Confirm that the current thread's priority is as expected.
+  EXPECT_EQ(kThreadPriority_Normal,
+            PlatformThread::GetThreadPriority(current_handle));
+
+  // Confirm that explictly exiting background mode while not in it fails...
+  EXPECT_FALSE(::SetThreadPriority(current_handle.platform_handle(),
+                                   THREAD_MODE_BACKGROUND_END));
+  // ... and results in the documented error.
+  EXPECT_EQ(ERROR_THREAD_MODE_NOT_BACKGROUND,
+            static_cast<int>(::GetLastError()));
+
+  PlatformThread::SetThreadPriority(current_handle, kThreadPriority_Background);
+  // Confirm that the current thread was in Windows' advanced background mode by
+  // successfully explictly exiting it.
+  EXPECT_TRUE(::SetThreadPriority(current_handle.platform_handle(),
+                                  THREAD_MODE_BACKGROUND_END));
+}
+#endif  // OS_WIN
+
 }  // namespace base