cc: Implement IndexRect for encapsulating tile indices.

The tiling data has many occurrences of left, right, top, bottom
indices. Encapsulating them in an object will help reduce the number
of variables passed in function or used as members in class.

BUG=624792
TESTS=IndexRectTest.*
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel

Review-Url: https://codereview.chromium.org/2350563002
Cr-Commit-Position: refs/heads/master@{#420256}

diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index b82d891..26b48a42d 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn

@@ -817,6 +817,7 @@
     "base/delayed_unique_notifier_unittest.cc",
     "base/float_quad_unittest.cc",
     "base/histograms_unittest.cc",
+    "base/index_rect_unittest.cc",
     "base/list_container_unittest.cc",
     "base/math_util_unittest.cc",
     "base/random_access_list_container_unittest.cc",