Stop recording UMA metrics for known reloc types.

chrome/browser/safe_browsing/incident_reporting/module_integrity_verifier_win.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/safe_browsing/incident_reporting/module_integrity_verifier_win.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
 #include "base/files/memory_mapped_file.h"
 #include "base/metrics/sparse_histogram.h"
@@ skipping 146 matching lines @@
                            state->disk_peimage,
                            &mem_code_addr,
                            &disk_code_addr,
                            &code_size))
     return false;
 
   // If not in the code section return true to continue to the next reloc.
   if (!AddrIsInCodeSection(address, mem_code_addr, code_size))
     return true;
 
-  UMA_HISTOGRAM_SPARSE_SLOWLY("SafeBrowsing.ModuleBaseRelocation", type);
-
   switch (type) {
-    case IMAGE_REL_BASED_HIGHLOW: {
-      AddBytesCorrectedByReloc(reinterpret_cast<uintptr_t>(address), state);
-      break;
-    }
-    case IMAGE_REL_BASED_ABSOLUTE:
+    case IMAGE_REL_BASED_ABSOLUTE:  // 0
       // Absolute type relocations are a noop, sometimes used to pad a section
       // of relocations.
       break;
-    default: {
+    case IMAGE_REL_BASED_HIGHLOW:  // 3
+      // The base relocation applies all 32 bits of the difference to the 32-bit
+      // field at offset.
+      AddBytesCorrectedByReloc(reinterpret_cast<uintptr_t>(address), state);
+      break;
+    case IMAGE_REL_BASED_DIR64:  // 10
+      // The base relocation applies the difference to the 64-bit field at
+      // offset.
+      // TODO(robertshield): Handle this type of reloc.
+      break;
+    default:
       // TODO(robertshield): Find a reliable description of the behaviour of the
       // remaining types of relocation and handle them.
+      UMA_HISTOGRAM_SPARSE_SLOWLY("SafeBrowsing.ModuleBaseRelocation", type);
       state->unknown_reloc_type = true;
       break;
-    }
   }
   return true;
 }
 
 bool EnumExportsCallback(const base::win::PEImage& mem_peimage,
                          DWORD ordinal,
                          DWORD hint,
                          LPCSTR name,
                          PVOID function_addr,
                          LPCSTR forward,
@@ skipping 95 matching lines @@
                                                      mem_code_addr,
                                                      code_size,
                                                      exports,
                                                      state,
                                                      modified_exports);
 
   return num_bytes_different ? MODULE_STATE_MODIFIED : MODULE_STATE_UNMODIFIED;
 }
 
 }  // namespace safe_browsing