mac: Don't require DYLD_LIBRARY_PATH to be set when using the shared build.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 65aa2d656bc257993b838619bd42ce9dc1e8a6d9..1440af8d0fe16c0c60a4ee2fcbb64b22424b53eb 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -1273,6 +1273,17 @@
       }, {  # else: branding!="Chrome"
         'defines': ['CHROMIUM_BUILD'],
       }],
+      ['OS=="mac" and component=="shared_library"', {
+        'xcode_settings': {
+          'DYLIB_INSTALL_NAME_BASE': '@rpath',
+          'LD_RUNPATH_SEARCH_PATHS': [
+            # For unbundled binaries.
+            '@loader_path/.',
+            # For bundled binaries, to get back from Binary.app/Contents/MacOS.
+            '@loader_path/../../..',
+          ],
+        },
+      }],
       ['branding=="Chrome" and (OS=="win" or OS=="mac")', {
         'defines': ['ENABLE_RLZ'],
       }],