Use tcmalloc on Linux

third_party/tcmalloc/README.dart

Index: third_party/tcmalloc/README.dart
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+Dart uses tcmalloc in the standalone VM on Linux.
+
+To roll tcmalloc forward:
+. Clone the gperftools git repo at the revision you want in a directory off
+  to the side.
+
+. Run a configure command similar to the one in the configure_command file in
+  this directory. It is up to you to determine if different flags are required
+  for the newer gperftools.
+
+. From that repo, copy src/config.h and src/gperftools/tcmalloc.h, and any other
+  generated header files to the include/ directory in this directory.
+
+. Make sure that include/config.h defines HAVE_UCONTEXT_H on Linux,
+
+. Update tcmalloc_sources.gypi, and tcmalloc.gyp if necessary. This may require
+  inspecting gperftools/Makefile.am to see any additional source files and
+  preprocessor defines (-D flags).
+
+. Update the DEPS file with the new git hash.
+
+. Build and run tests for Debug, Release, and Product builds for ia32, x64, mips
+  and arm for Linux and any other OSs that are supported.