Implement committed physical memory stats for Linux.

src/platform-solaris.cc

Index: src/platform-solaris.cc
diff --git a/src/platform-solaris.cc b/src/platform-solaris.cc
index 4248ea214faa9b7d2c23ec4527d668d4ce542e2c..2ab3feeae3b961e8b457bd80deca7e41344da175 100644
--- a/src/platform-solaris.cc
+++ b/src/platform-solaris.cc
@@ -448,6 +448,13 @@ bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
 }
 
 
+bool VirtualMemory::CommittedPhysicalSizeInRegion(
+    void* base, size_t size, size_t* physical) {
+  // TODO(alph): implement for the platform.
+  return false;
+}
+
+
 class Thread::PlatformData : public Malloced {
  public:
   PlatformData() : thread_(kNoThread) {  }