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

Review URL: https://codereview.chromium.org/1101513003

Cr-Commit-Position: refs/heads/master@{#326705}

device/BUILD.gn

@@ -112,5 +112,13 @@ 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',
+                  ],
+                },
+              }],
+            ],
           },
         }],
       ],