mac: Weakly link against the CoreBluetooth framework. (attempt #2)

The first attempt to land this CL failed because there weas a missing import in
device/BUILD.gn.

> mac: Weakly link against the CoreBluetooth framework.
>
> In the OSX 10.10 SDK, CoreBluetooth became a top level framework. Previously,
> it was nested in IOBluetooth. In order for Chrome to run on OSes older than OSX
> 10.10, the top level CoreBluetooth framework must be weakly linked.
>
> BUG=463170
> Committed: https://crrev.com/9fde3e00865650009c7e85fcb7157719372b97a8
> Cr-Commit-Position: refs/heads/master@{#326705}

BUG=463170
TBR=rsesek@chromium.org, keybuk@chromium.org

Review URL: https://codereview.chromium.org/1056313004

Cr-Commit-Position: refs/heads/master@{#327065}

device/BUILD.gn

@@ -5,6 +5,10 @@
 import("//build/config/features.gni")
 import("//testing/test.gni")
 
+if (is_mac) {
+  import("//build/config/mac/mac_sdk.gni")
+}
+
 is_linux_without_udev = is_linux && !use_udev
 is_linux_without_dbus = is_linux && !use_dbus
 
@@ -112,5 +116,13 @@ test("device_unittests") {
 
   if (is_mac) {
     libs = [ "IOBluetooth.framework" ]
+
+    # In the OSX 10.10 SDK, CoreBluetooth became a top level framework.
+    # Previously, it was nested in IOBluetooth. In order for Chrome to run on
+    # OSes older than OSX 10.10, the top level CoreBluetooth framework must be
+    # weakly linked.
+    if (mac_sdk_version == "10.10") {
+      ldflags = [ "-weak_framework CoreBluetooth" ]
+    }
   }
 }

device/bluetooth/bluetooth.gyp

@@ -152,6 +152,19 @@
             'libraries': [
               '$(SDKROOT)/System/Library/Frameworks/IOBluetooth.framework',
             ],
+            'conditions': [
+              ['mac_sdk == "10.10"', {
+                'xcode_settings': {
+                  # In the OSX 10.10 SDK, CoreBluetooth became a top level
+                  # framework. Previously, it was nested in IOBluetooth. In
+                  # order for Chrome to run on OSes older than OSX 10.10, the
+                  # top level CoreBluetooth framework must be weakly linked.
+                  'OTHER_LDFLAGS': [
+                    '-weak_framework CoreBluetooth',
+                  ],
+                },
+              }],
+            ],
           },
         }],
       ],