Add multiprocessing.cpu_count access to platform module.

recipe_modules/platform/api.py

Index: recipe_modules/platform/api.py
diff --git a/recipe_modules/platform/api.py b/recipe_modules/platform/api.py
index ecd5f673cc345f4165edc7bc51bf8313e44e5bfa..ded9f6ec947ec1395aaeea1a3623a46710303b09 100644
--- a/recipe_modules/platform/api.py
+++ b/recipe_modules/platform/api.py
@@ -4,6 +4,7 @@
 
 import sys
 import platform
+import multiprocessing
 
 from recipe_engine import recipe_api
 
@@ -44,6 +45,7 @@ class PlatformApi(recipe_api.RecipeApi):
       # Default to linux/64, unless test case says otherwise.
       self._name = norm_plat(self._test_data.get('name', 'linux'))
       self._bits = norm_bits(self._test_data.get('bits', 64))
+      self._cpu_count = self._test_data.get('cpu_count', 2)
     else:  # pragma: no cover
       # platform.machine is based on running kernel. It's possible to use 64-bit
       # kernel with 32-bit userland, e.g. to give linker slightly more memory.
@@ -60,6 +62,8 @@ class PlatformApi(recipe_api.RecipeApi):
             platform.architecture()[0] == '64bit'):
         self._bits = 64
 
+      self._cpu_count = multiprocessing.cpu_count()
+
   @property
   def is_win(self):
     return self.name == 'win'
@@ -86,6 +90,11 @@ class PlatformApi(recipe_api.RecipeApi):
   def arch(self):
     return self._arch
 
+  @property
+  def cpu_count(self):
+    """The number of CPU cores, according to multiprocessing.cpu_count()."""
+    return self._cpu_count
+
   @staticmethod
   def normalize_platform_name(platform):
     """One of python's sys.platform values -> 'win', 'linux' or 'mac'."""