bug 1409721 - move firefox-l10n.js to moz.build. r=nalexander

This is a fairly straightforward application of LOCALIZED_PP_FILES.

The extra layer of PREF_DIR can be removed because all of browser
has DIST_SUBDIR set due to it being exported in browser/moz.build, and
that means that PREF_DIR is always defaults/preferences here:
https://dxr.mozilla.org/mozilla-central/rev/f41930a869a84af81df1a88d8e82323ff3a6509a/config/rules.mk#1205

Additionally, it turns out that PREF_PPFLAGS is not set anywhere in the tree,
so I simply left it out of the translation.

MozReview-Commit-ID: 874EeTZRdLI

--HG--
extra : rebase_source : e6950c3528cdc655d290189641e2d54adc0422ae
extra : source : baa2f0ec9b1d2bb0e8c2e55ad38039a364637439

browser/locales/Makefile.in

@@ -28,11 +28,6 @@ ifdef NIGHTLY_BUILD
 export EN_US_BINARY_URL ?= https://archive.mozilla.org/pub/firefox/nightly/latest-mozilla-central
 endif
 
-L10N_PREF_JS_EXPORTS = $(call MERGE_FILE,firefox-l10n.js)
-L10N_PREF_JS_EXPORTS_PATH = $(FINAL_TARGET)/$(PREF_DIR)
-L10N_PREF_JS_EXPORTS_FLAGS = $(PREF_PPFLAGS) --silence-missing-directive-warnings
-PP_TARGETS += L10N_PREF_JS_EXPORTS
-
 ifneq (,$(filter cocoa,$(MOZ_WIDGET_TOOLKIT)))
 MOZ_PKG_MAC_DSSTORE=$(ABS_DIST)/branding/dsstore
 MOZ_PKG_MAC_BACKGROUND=$(ABS_DIST)/branding/background.png

browser/locales/moz.build

@@ -6,6 +6,9 @@
 
 JAR_MANIFESTS += ['jar.mn']
 
+# If DIST_SUBDIR ever gets unset in browser this path might be wrong due to PREF_DIR changing.
+LOCALIZED_PP_FILES.defaults.preferences += ['en-US/firefox-l10n.js']
+
 if CONFIG['MOZ_CRASHREPORTER']:
     LOCALIZED_FILES += ['en-US/crashreporter/crashreporter-override.ini']