Move a bunch of child-only code from content/common to content/child

content/gpu/gpu_main.cc

Index: content/gpu/gpu_main.cc
diff --git a/content/gpu/gpu_main.cc b/content/gpu/gpu_main.cc
index 2bfd51f224df6a87a92185bf1c018e0078fb7736..acc7998fe10b15483bd449c521d24a8f6419b4bc 100644
--- a/content/gpu/gpu_main.cc
+++ b/content/gpu/gpu_main.cc
@@ -15,6 +15,7 @@
 #include "base/stringprintf.h"
 #include "base/threading/platform_thread.h"
 #include "build/build_config.h"
+#include "content/common/debug_util.h"
 #include "content/common/gpu/gpu_config.h"
 #include "content/common/sandbox_linux.h"
 #include "content/gpu/gpu_child_thread.h"
@@ -69,7 +70,7 @@ int GpuMain(const MainFunctionParams& parameters) {
 
   const CommandLine& command_line = parameters.command_line;
   if (command_line.HasSwitch(switches::kGpuStartupDialog)) {
-    ChildProcess::WaitForDebugger("Gpu");
+    WaitForDebugger("Gpu");
   }
 
   if (!command_line.HasSwitch(switches::kSingleProcess)) {