Added flags for PrintBrowser mode

printing/features/BUILD.gn

Index: printing/features/BUILD.gn
diff --git a/printing/features/BUILD.gn b/printing/features/BUILD.gn
index cdcfd794774c97648b2ce43f6eae4ec841b18d23..134844d78405f2a1b3f0d1f6ddcacdf616d1c7e9 100644
--- a/printing/features/BUILD.gn
+++ b/printing/features/BUILD.gn
@@ -12,6 +12,11 @@ import("//printing/features/features.gni")
 buildflag_header("features") {
   header = "features.h"
 
+  # enable_print_browser requires enable_print_preview
+  if (enable_print_browser) {
+    enable_print_preview = true

[skau, 2016/12/16 18:05:53]

instead of forcing print_preview to be true, can you require that it's true and
throw an error otherwise.  This behavior seems surprising.

+  }
+
   # Convenience define for ENABLE_BASIC_PRINTING || ENABLE_PRINT_PREVIEW.
   enable_printing = enable_basic_printing || enable_print_preview
 
@@ -19,5 +24,6 @@ buildflag_header("features") {
     "ENABLE_PRINTING=$enable_printing",
     "ENABLE_BASIC_PRINTING=$enable_basic_printing",
     "ENABLE_PRINT_PREVIEW=$enable_print_preview",
+    "ENABLE_PRINT_BROWSER=$enable_print_browser",
   ]
 }