Move platform_thread to base/threading and put in the base namespace. I left ...

chrome/browser/printing/printing_layout_uitest.cc

Index: chrome/browser/printing/printing_layout_uitest.cc
===================================================================
--- chrome/browser/printing/printing_layout_uitest.cc	(revision 70328)
+++ chrome/browser/printing/printing_layout_uitest.cc	(working copy)
@@ -164,7 +164,7 @@
       }
       if (found_emf && found_prn)
         break;
-      PlatformThread::Sleep(100);
+      base::PlatformThread::Sleep(100);
     }
     EXPECT_TRUE(found_emf) << ".PRN file is: " << prn_file;
     EXPECT_TRUE(found_prn) << ".EMF file is: " << emf_file;
@@ -256,13 +256,13 @@
           break;
         }
       }
-      PlatformThread::Sleep(10);
+      base::PlatformThread::Sleep(10);
     }
 
     // Now verify that it indeed closed itself.
     while (IsWindow(dialog_window)) {
       CloseDialogWindow(dialog_window);
-      PlatformThread::Sleep(10);
+      base::PlatformThread::Sleep(10);
     }
   }