Use new sanitizer coverage flags.

-fsanitize-coverage={edge,bb,func} are deprecated.

-fsanitize-coverage={edge,bb,func},trace-pc-guard should be used instead (edge is default).

BUG=651540

Review-Url: https://codereview.chromium.org/2860643002
Cr-Commit-Position: refs/heads/master@{#468993}

build/config/sanitizers/sanitizers.gni

@@ -92,10 +92,10 @@ declare_args() {
 
   # Value for -fsanitize-coverage flag. Setting this causes
   # use_sanitizer_coverage to be enabled.
-  # Default value when unset and use_afl=true:
-  # trace-pc
+  # Default value when unset and use_afl=true or use_libfuzzer=true:
+  #     trace-pc-guard
   # Default value when unset and use_sanitizer_coverage=true:
-  #     edge,indirect-calls,8bit-counters
+  #     trace-pc-guard,indirect-calls
   sanitizer_coverage_flags = ""
 
   # Keep symbol level when building with sanitizers. When sanitizers are
@@ -154,7 +154,7 @@ declare_args() {
 if ((use_afl || use_libfuzzer) && sanitizer_coverage_flags == "") {
   sanitizer_coverage_flags = "trace-pc-guard"
 } else if (use_sanitizer_coverage && sanitizer_coverage_flags == "") {
-  sanitizer_coverage_flags = "edge,indirect-calls,8bit-counters"
+  sanitizer_coverage_flags = "trace-pc-guard,indirect-calls"
 }
 
 using_sanitizer =

tools/mb/mb_config.pyl

@@ -1688,7 +1688,7 @@
     },
 
     'edge': {
-      'gn_args': 'sanitizer_coverage_flags="edge"',
+      'gn_args': 'sanitizer_coverage_flags="trace-pc-guard"',
     },
 
     # This mixin is used to force configs that use it to fail. It