--- a/toolkit/library/Makefile.in
+++ b/toolkit/library/Makefile.in
@@ -61,60 +61,16 @@ EXTRA_DSO_LDOPTS += -Wl,-version-script,
 symverscript: symverscript.in
 	$(call py_action,preprocessor, \
 		-DVERSION='$(LIBRARY_NAME)$(MOZILLA_SYMBOLVERSION)' $< -o $@)
 
 EXTRA_DEPS += symverscript
 endif
 endif
 
-# component libraries
-ifdef MOZ_JSDEBUGGER
-DEFINES += -DMOZ_JSDEBUGGER
-endif
-
-ifdef MOZ_PREF_EXTENSIONS
-DEFINES += -DMOZ_PREF_EXTENSIONS
-endif
-
-ifdef MOZ_AUTH_EXTENSION
-DEFINES += -DMOZ_AUTH_EXTENSION
-endif
-
-ifdef MOZ_PERMISSIONS
-DEFINES += -DMOZ_PERMISSIONS
-endif
-
-ifdef MOZ_UNIVERSALCHARDET
-DEFINES += -DMOZ_UNIVERSALCHARDET
-endif
-
-ifeq (,$(filter android gonk qt os2 cocoa windows,$(MOZ_WIDGET_TOOLKIT)))
-ifdef MOZ_XUL
-DEFINES += -DMOZ_FILEVIEW
-endif
-endif
-
-# Platform-specific icon channel stuff - supported mostly-everywhere
-ifneq (,$(filter windows os2 mac cocoa gtk2 gtk3 qt android,$(MOZ_WIDGET_TOOLKIT)))
-DEFINES += -DICON_DECODER
-endif
-
-ifdef MOZ_SPELLCHECK
-DEFINES += -DMOZ_SPELLCHECK
-endif
-
-ifdef MOZ_ZIPWRITER
-DEFINES += -DMOZ_ZIPWRITER
-endif
-
-ifdef MOZ_GIO_COMPONENT
-DEFINES += -DMOZ_GIO_COMPONENT
-endif
-
 ifdef MOZ_APP_COMPONENT_LIBS
 COMPONENT_LIBS += $(MOZ_APP_COMPONENT_LIBS)
 endif
 
 ifeq ($(MOZ_WIDGET_TOOLKIT),cocoa)
 OS_LIBS += -framework OpenGL -lcups
 endif
 
@@ -388,22 +344,16 @@ LOCAL_INCLUDES += \
   $(NULL)
 
 OS_LIBS += $(LIBICONV)
 
 ifeq ($(MOZ_WIDGET_TOOLKIT),windows)
 OS_LIBS += $(call EXPAND_LIBNAME,usp10 oleaut32)
 endif
 
-ifdef MOZ_DEBUG
-ifdef ENABLE_TESTS
-DEFINES += -DENABLE_LAYOUTDEBUG
-endif
-endif
-
 ifeq (WINNT_1,$(OS_TARGET)_$(MOZ_PROFILE_USE))
 # Wrap linker to measure peak virtual memory usage.
 LD := $(PYTHON) $(topsrcdir)/build/link.py $(CURDIR)/linker-vsize $(LD)
 endif
 
 ifndef LINK_GTEST
 ifdef COMPILE_ENVIRONMENT
 libs:: $(FINAL_TARGET)/dependentlibs.list

--- a/toolkit/library/moz.build
+++ b/toolkit/library/moz.build
@@ -10,13 +10,42 @@ SOURCES += [
     'nsStaticXULComponents.cpp',
 ]
 
 if CONFIG['OS_ARCH'] == 'WINNT':
     SOURCES += [
         'nsDllMain.cpp',
     ]
 
+# component libraries
+additional_defines = (
+    'MOZ_AUTH_EXTENSION',
+    'MOZ_GIO_COMPONENT',
+    'MOZ_JSDEBUGGER',
+    'MOZ_PERMISSIONS',
+    'MOZ_PREF_EXTENSIONS',
+    'MOZ_SPELLCHECK',
+    'MOZ_UNIVERSALCHARDET',
+    'MOZ_ZIPWRITER',
+)
+
+for var in additional_defines:
+    if CONFIG[var]:
+        DEFINES[var] = True
+
+if CONFIG['MOZ_DEBUG'] and CONFIG['ENABLE_TESTS']:
+    DEFINES['ENABLE_LAYOUTDEBUG'] = True
+
+if CONFIG['MOZ_WIDGET_TOOLKIT'] not in ('android', 'gonk', 'qt', 'os2',
+                                        'cocoa', 'windows') and \
+   CONFIG['MOZ_XUL']:
+    DEFINES['MOZ_FILEVIEW'] = True
+
+# Platform-specific icon channel stuff - supported mostly-everywhere
+if CONFIG['MOZ_WIDGET_TOOLKIT'] in ('windows', 'os2', 'mac', 'cocoa',
+                                    'gtk2', 'gtk3', 'qt', 'android'):
+    DEFINES['ICON_DECODER'] = True
+
 FAIL_ON_WARNINGS = True
 
 MSVC_ENABLE_PGO = True
 
 FORCE_SHARED_LIB = True