Introduce background Download process to android

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index b87df7f8f2d4a75c01367d7858920e4ec9fd1d76..8fb6013ebb7f2a269c62e30c80b0678b5b17f812 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -298,6 +298,9 @@ const char kDisableZeroCopy[]                = "disable-zero-copy";
 // based tests.
 const char kDomAutomationController[]       = "dom-automation";
 
+// Causes the process to run as a download subprocess.
+const char kDownloadProcess[]               = "download";
+
 // Enable antialiasing on 2d canvas clips (as opposed to draw operations)
 const char kEnable2dCanvasClipAntialiasing[] = "enable-2d-canvas-clip-aa";