Refresh cache when core.themes changes

Previously this wasn't needed because a new cache was created for each
stylesheet loaded.

src/less-compile-cache.coffee

@@ -11,21 +11,25 @@ class LessCompileCache
 
   @cacheDir: path.join(tmpDir, 'atom-compile-cache', 'less')
 
-  constructor: ({resourcePath}) ->
+  constructor: ({resourcePath, importPaths}) ->
     @lessSearchPaths = [
       path.join(resourcePath, 'static', 'variables')
       path.join(resourcePath, 'static')
     ]
 
+    if importPaths?
+      importPaths = importPaths.concat(@lessSearchPaths)
+    else
+      importPaths = @lessSearchPaths
+
     @cache = new LessCache
       cacheDir: @constructor.cacheDir
-      importPaths: @getImportPaths()
+      importPaths: importPaths
       resourcePath: resourcePath
       fallbackDir: path.join(resourcePath, 'less-compile-cache')
 
-    @subscribe atom.themes, 'reloaded', => @cache.setImportPaths(@getImportPaths())
-
-  getImportPaths: -> atom.themes.getImportPaths().concat(@lessSearchPaths)
+  setImportPaths: (importPaths=[]) ->
+    @cache.setImportPaths(importPaths.concat(@lessSearchPaths))
 
   read: (stylesheetPath) -> @cache.readFileSync(stylesheetPath)
 

src/theme-manager.coffee

@@ -56,6 +56,7 @@ class ThemeManager
       themeNames = _.clone(themeNames).reverse()
 
       @packageManager.activatePackage(themeName) for themeName in themeNames
+      @refreshLessCache()
       @loadUserStylesheet()
       @reloadBaseStylesheets()
       @emit('reloaded')
@@ -66,6 +67,10 @@ class ThemeManager
     @packageManager.deactivatePackage(pack.name) for pack in @getActiveThemes()
     null
 
+  # Internal-only:
+  refreshLessCache: ->
+    @lessCache?.setImportPaths(@getImportPaths())
+
   # Public: Set the list of enabled themes.
   #
   # * enabledThemeNames: An {Array} of {String} theme names.
@@ -148,7 +153,7 @@ class ThemeManager
   loadLessStylesheet: (lessStylesheetPath) ->
     unless @lessCache?
       LessCompileCache = require './less-compile-cache'
-      @lessCache = new LessCompileCache({@resourcePath})
+      @lessCache = new LessCompileCache({@resourcePath, importPaths: @getImportPaths()})
 
     try
       @lessCache.read(lessStylesheetPath)