Add empty implementation of GetSystemMemoryInfo for IOS.

base/process/process_metrics_ios.cc

Index: base/process/process_metrics_ios.cc
diff --git a/base/process/process_metrics_ios.cc b/base/process/process_metrics_ios.cc
index 07f2c8de1d46ff41ed88214b0ac624f94f5eb0d9..135ef43c06c12a5a850c39a81fc3a19a6fa2a39a 100644
--- a/base/process/process_metrics_ios.cc
+++ b/base/process/process_metrics_ios.cc
@@ -23,6 +23,11 @@ bool GetTaskInfo(task_basic_info_64* task_info_data) {
 
 }  // namespace
 
+SystemMemoryInfoKB::SystemMemoryInfoKB() {
+  total = 0;
+  free = 0;
+}
+
 ProcessMetrics::ProcessMetrics(ProcessHandle process) {}
 
 ProcessMetrics::~ProcessMetrics() {}
@@ -82,4 +87,11 @@ size_t GetSystemCommitCharge() {
   return 0;
 }
 
+// Bytes committed by the system.
+bool GetSystemMemoryInfo(SystemMemoryInfoKB* meminfo) {
+  // Unimplemented. Must enable unittest for IOS when this gets implemented.
+  NOTIMPLEMENTED();
+  return false;
+}
+
 }  // namespace base