Enable automatic rescaling in bench_pictures

bench_pictures with "--device gpu" is failing because we're trying to allocate
too much GPU memory.  Move the recently-added scaling code into picture_utils
and share it between render_pictures and bench_pictures.
Review URL: https://codereview.appspot.com/6495125

git-svn-id: http://skia.googlecode.com/svn/trunk@5543 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/tools.gyp b/gyp/tools.gyp
index 28456a2..371ecd2 100644
--- a/gyp/tools.gyp
+++ b/gyp/tools.gyp
@@ -143,6 +143,7 @@
       'type': 'static_library',
       'sources': [
         '../tools/picture_utils.cpp',
+        '../tools/picture_utils.h',
       ],
       'dependencies': [
         'core.gyp:core',