Shared Raster Worker Threads

cc/base/switches.cc

Index: cc/base/switches.cc
diff --git a/cc/base/switches.cc b/cc/base/switches.cc
index ddba9cbd4449b52cb8edd870a77dccc45faafb35..ab7cf70c8326c2a8f45ff68e11bb287e22ecb202 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -5,6 +5,8 @@
 #include "cc/base/switches.h"
 
 #include "base/command_line.h"
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
 
 namespace cc {
 namespace switches {
@@ -186,6 +188,26 @@ bool CheckGPURasterizationStatus() {
   return command_line.HasSwitch(switches::kEnableGPURasterization);
 }
 
+size_t CheckNumRasterThreads() {
+  const int kMinRasterThreads = 1;
+  const int kMaxRasterThreads = 64;
+  const int kDefaultNumRasterThreads = 1;
+
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(switches::kNumRasterThreads)) {
+    std::string string_value =
+        command_line.GetSwitchValueASCII(switches::kNumRasterThreads);
+    int num_threads = kDefaultNumRasterThreads;
+    if (base::StringToInt(string_value, &num_threads) &&
+        num_threads >= kMinRasterThreads && num_threads <= kMaxRasterThreads)
+      return num_threads;
+
+    LOG(WARNING) << "Failed to parse switch " <<
+                    switches::kNumRasterThreads  << ": " << string_value;
+  }
+  return kDefaultNumRasterThreads;
+}
+
 }  // namespace
 
 bool IsImplSidePaintingEnabled() {
@@ -209,5 +231,10 @@ bool IsMapImageEnabled() {
   return false;
 }
 
+size_t GetNumRasterThreads() {
+  static size_t num_raster_threads = CheckNumRasterThreads();
+  return num_raster_threads;
+}
+
 }  // namespace switches
 }  // namespace cc