Make the dependency of enable_print_preview and enable_pdf explicit

build/config/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/allocator.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/sanitizers/sanitizers.gni")
@@ skipping 51 matching lines @@
   }
   if (enable_browser_cdms) {
     # TODO(brettw) should probably be "=1"
     defines += [ "ENABLE_BROWSER_CDMS" ]
   }
   if (enable_plugins) {
     defines += [ "ENABLE_PLUGINS=1" ]
   }
   if (enable_pdf) {
     defines += [ "ENABLE_PDF=1" ]
+  } else {
+    assert(!is_win, "set enable_pdf=true on Windows.")

[Lei Zhang, 2016/05/18 21:43:37]

I'd prefer we remove this check, and put all the checks below in the printing
block. Essentially:

- Windows basic printing requires PDF
- Print preview requires PDF

[Wei Li, 2016/05/19 17:13:30]

Done.

   }
   if (enable_basic_printing || enable_print_preview) {
     # Convenience define for ENABLE_BASIC_PRINTING || ENABLE_PRINT_PREVIEW.
     defines += [ "ENABLE_PRINTING=1" ]
     if (enable_basic_printing) {
       # Enable basic printing support and UI.
       defines += [ "ENABLE_BASIC_PRINTING=1" ]
     }
     if (enable_print_preview) {
       # Enable printing with print preview.
       # Can be defined without ENABLE_BASIC_PRINTING.
       defines += [ "ENABLE_PRINT_PREVIEW=1" ]
+      assert(enable_pdf,
+             "Print preview depends on pdf module: set enable_pdf=true.")
     }
   }
   if (enable_spellcheck) {
     defines += [ "ENABLE_SPELLCHECK=1" ]
   }
   if (use_browser_spellchecker) {
     defines += [ "USE_BROWSER_SPELLCHECKER=1" ]
   }
   if (dcheck_always_on) {
     defines += [ "DCHECK_ALWAYS_ON=1" ]
@@ skipping 352 matching lines @@
       # file doesn't exist, no error will be generated (probably MS tested this
       # case but forgot the other one?). To reproduce this error, do a build,
       # then delete the precompile.c.obj file, then build again.
       cflags_c = [ "/wd4206" ]
     } else if (is_mac) {
       precompiled_header = "build/precompile.h"
       precompiled_source = "//build/precompile.h"
     }
   }
 }