Create libsampler as V8 sampler library.

src/v8.gyp

Index: src/v8.gyp
diff --git a/src/v8.gyp b/src/v8.gyp
index c5e214acdf5805f308132dc87fe4438cb41a52c5..f9478c52578920105a816fb713e2dd7af4804df3 100644
--- a/src/v8.gyp
+++ b/src/v8.gyp
@@ -381,6 +381,7 @@
       'type': 'static_library',
       'dependencies': [
         'v8_libbase',
+        'v8_libsampler',
       ],
       'variables': {
         'optimize': 'max',
@@ -1001,8 +1002,6 @@
         'profiler/profile-generator-inl.h',
         'profiler/profile-generator.cc',
         'profiler/profile-generator.h',
-        'profiler/sampler.cc',
-        'profiler/sampler.h',
         'profiler/sampling-heap-profiler.cc',
         'profiler/sampling-heap-profiler.h',
         'profiler/strings-storage.cc',
@@ -1940,6 +1939,38 @@
       },
     },
     {
+      'target_name': 'v8_libsampler',
+      'type': 'static_library',
+      'variables': {
+        'optimize': 'max',
+      },
+      'dependencies': [
+        'v8_libbase',
+      ],
+      'include_dirs+': [
+        '..',
+        '../include',
+      ],
+      'sources': [
+        'libsampler/hashmap.h',
+        'libsampler/utils.h',
+        'libsampler/v8-sampler.cc',
+        'libsampler/v8-sampler.h'
+      ],
+      'conditions': [
+        ['want_separate_host_toolset==1', {
+          'toolsets': ['host', 'target'],
+        }, {
+          'toolsets': ['target'],
+        }],
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          '../include',
+        ],
+      },
+    },
+    {
       'target_name': 'natives_blob',
       'type': 'none',
       'conditions': [