Move Device Sensors client files from Blink to //device/sensors client lib

device/sensors/public/cpp/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("cpp") {
+# This target contains only those files that are shared by the Device Sensors
+# implementation and all Device Sensors clients, including Blink. Add a file
+# here only if it meets the following constraints:
+# (1) It is *necessary* to use the file to consume Device Sensors (the
+# current files define structs that are used as a consistent interpretation of
+# shared memory by the Device Sensor and its clients).
+# (2) The file has no dependencies on the STL or Chromium code and will not
+# grow them over time (the current  files are POD structs and will necessarily
+# stay that way due to their above-described purpose).
+# If a file does not meet these constraints, it cannot be used by the Blink
+# client and should be placed in the "full" target below. Similarly, clients
+# without Blink's constraints should depend on the "full" target below rather
+# than this one.
+# Consult {platform-architecture-dev, services-dev}@chromium.org in the case
+# of any uncertainty.
+source_set("shared_with_blink") {
+  sources = [
+    "motion_data.cc",
+    "motion_data.h",
+    "orientation_data.cc",
+    "orientation_data.h",
+  ]
+  # Do not add deps here per the above comment.
+}
+
+# This target is a superset of the above one that contains additional optional
+# files available to Device Sensors clients. This target may bring in
+# dependencies on the STL and Chromium code.
+source_set("full") {
   sources = [
     "device_light_data.h",
     "device_light_hardware_buffer.h",
     "device_motion_hardware_buffer.h",
     "device_orientation_hardware_buffer.h",
     "device_sensors_consts.h",
     "device_util_mac.cc",
     "device_util_mac.h",
   ]
 
   public_deps = [
+    ":shared_with_blink",
     "//device/base/synchronization",
-    "//third_party/WebKit/public:blink_headers",
   ]
 }