Created placeholders for MallocHooks implementation and added define DART_USE_TCMALLOC to specifiy …

runtime/vm/vm.gypi

Index: runtime/vm/vm.gypi
diff --git a/runtime/vm/vm.gypi b/runtime/vm/vm.gypi
index a8c0e74ac4b04cbf916dea3ac8929de966de5729..1371285b1ee28c42814071b01ae2f5b962f82f22 100644
--- a/runtime/vm/vm.gypi
+++ b/runtime/vm/vm.gypi
@@ -61,6 +61,13 @@
             ],
           },
         }],
+        # The following condition should be kept in sync with the corresponding
+        # configurations in runtime/bin/bin.gypi.
+	['OS == "linux" and asan == 0 and msan == 0 and tsan == 0', {
+          'defines': [
+            'DART_USE_TCMALLOC'
+          ],
+        }],
         ['OS=="android" and _toolset=="host"', {
           'link_settings': {
             'libraries': [
@@ -105,6 +112,13 @@
             ],
           },
         }],
+        # The following condition should be kept in sync with the corresponding
+        # configurations in runtime/bin/bin.gypi.
+        ['OS == "linux" and asan == 0 and msan == 0 and tsan == 0', {
+          'defines': [
+            'DART_USE_TCMALLOC'
+          ],
+        }],
         ['OS=="android" and _toolset=="host"', {
           'link_settings': {
             'libraries': [
@@ -149,6 +163,13 @@
             ],
           },
         }],
+        # The following condition should be kept in sync with the corresponding
+        # configurations in runtime/bin/bin.gypi.
+        ['OS == "linux" and asan == 0 and msan == 0 and tsan == 0', {
+          'defines': [
+            'DART_USE_TCMALLOC'
+          ],
+        }],
         ['OS=="android" and _toolset=="host"', {
           'link_settings': {
             'libraries': [
@@ -194,6 +215,13 @@
             ],
           },
         }],
+        # The following condition should be kept in sync with the corresponding
+        # configurations in runtime/bin/bin.gypi.
+        ['OS == "linux" and asan == 0 and msan == 0 and tsan == 0', {
+          'defines': [
+            'DART_USE_TCMALLOC'
+          ],
+        }],
         ['OS=="android" and _toolset=="host"', {
           'link_settings': {
             'libraries': [