[Benchmarking] Reshard Nexus 5 Perf to use half the devices.

Some of the reimaging to android M didn't work.

Do not revert this change if it appears to
cause a perf regression. That regression
was likely caused by upgrading the devices from
Android version K to Android version M. DO
NOT REVERT this change.

TBR=johnchen@chromium.org

Bug: 1041944
Change-Id: Idbcc6de3bd69dfe2724e146dfee1b25e32518f0c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2104453
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750446}

testing/buildbot/chromium.perf.json

@@ -36,7 +36,7 @@
           "ignore_task_failure": false,
           "io_timeout": 21600,
           "service_account": "chrome-tester@chops-service-accounts.iam.gserviceaccount.com",
-          "shards": 16
+          "shards": 8
         },
         "trigger_script": {
           "args": [

tools/perf/core/bot_platforms.py

@@ -454,7 +454,7 @@ ANDROID_GO_WEBVIEW = PerfPlatform(
     run_reference_build=False)
 ANDROID_NEXUS_5 = PerfPlatform(
     'Android Nexus5 Perf', 'Android KOT49H', _ANDROID_NEXUS_5_BENCHMARK_CONFIGS,
-    16, 'android', executables=_ANDROID_NEXUS_5_EXECUTABLE_CONFIGS)
+    8, 'android', executables=_ANDROID_NEXUS_5_EXECUTABLE_CONFIGS)
 ANDROID_NEXUS_5X_WEBVIEW = PerfPlatform(
     'Android Nexus5X WebView Perf', 'Android AOSP MOB30K',
     _ANDROID_NEXUS_5X_WEBVIEW_BENCHMARK_CONFIGS, 16, 'android',

tools/perf/core/shard_maps/android_nexus5_perf_map.json

@@ -2,7 +2,7 @@
     "0": {
         "benchmarks": {
             "loading.mobile": {
-                "end": 1,
+                "end": 3,
                 "abridged": true
             }
         },
@@ -19,32 +19,14 @@
         }
     },
     "1": {
-        "benchmarks": {
-            "loading.mobile": {
-                "begin": 1,
-                "end": 3,
-                "abridged": true
-            }
-        }
-    },
-    "2": {
         "benchmarks": {
             "loading.mobile": {
                 "begin": 3,
-                "end": 5,
                 "abridged": true
             }
         }
     },
-    "3": {
-        "benchmarks": {
-            "loading.mobile": {
-                "begin": 5,
-                "abridged": true
-            }
-        }
-    },
-    "4": {
+    "2": {
         "benchmarks": {
             "startup.mobile": {
                 "end": 1,
@@ -52,10 +34,7 @@
             }
         }
     },
-    "5": {
-        "benchmarks": {}
-    },
-    "6": {
+    "3": {
         "benchmarks": {
             "startup.mobile": {
                 "begin": 1,
@@ -64,74 +43,40 @@
             }
         }
     },
-    "7": {
-        "benchmarks": {}
-    },
-    "8": {
+    "4": {
         "benchmarks": {
             "startup.mobile": {
                 "begin": 2,
                 "abridged": true
-            }
-        }
-    },
-    "9": {
-        "benchmarks": {
+            },
             "system_health.common_mobile": {
                 "end": 2,
                 "abridged": true
             }
         }
     },
-    "10": {
+    "5": {
         "benchmarks": {
             "system_health.common_mobile": {
                 "begin": 2,
-                "end": 3,
-                "abridged": true
-            }
-        }
-    },
-    "11": {
-        "benchmarks": {
-            "system_health.common_mobile": {
-                "begin": 3,
                 "end": 5,
                 "abridged": true
             }
         }
     },
-    "12": {
+    "6": {
         "benchmarks": {
             "system_health.common_mobile": {
                 "begin": 5,
-                "end": 7,
-                "abridged": true
-            }
-        }
-    },
-    "13": {
-        "benchmarks": {
-            "system_health.common_mobile": {
-                "begin": 7,
                 "end": 10,
                 "abridged": true
             }
         }
     },
-    "14": {
+    "7": {
         "benchmarks": {
             "system_health.common_mobile": {
                 "begin": 10,
-                "end": 11,
-                "abridged": true
-            }
-        }
-    },
-    "15": {
-        "benchmarks": {
-            "system_health.common_mobile": {
-                "begin": 11,
                 "abridged": true
             },
             "system_health.webview_startup": {
@@ -146,25 +91,17 @@
     },
     "extra_infos": {
         "num_stories": 26,
-        "predicted_min_shard_time": 0,
-        "predicted_min_shard_index": 5,
-        "predicted_max_shard_time": 896.0,
+        "predicted_min_shard_time": 704.0,
+        "predicted_min_shard_index": 1,
+        "predicted_max_shard_time": 1084.0,
         "predicted_max_shard_index": 4,
-        "shard #0": 556.0,
-        "shard #1": 416.0,
-        "shard #2": 488.0,
-        "shard #3": 216.0,
-        "shard #4": 896.0,
-        "shard #5": 0,
-        "shard #6": 804.0,
-        "shard #7": 0,
-        "shard #8": 688.0,
-        "shard #9": 396.0,
-        "shard #10": 576.0,
-        "shard #11": 456.0,
-        "shard #12": 364.0,
-        "shard #13": 548.0,
-        "shard #14": 360.0,
-        "shard #15": 436.0
+        "shard #0": 972.0,
+        "shard #1": 704.0,
+        "shard #2": 896.0,
+        "shard #3": 804.0,
+        "shard #4": 1084.0,
+        "shard #5": 1032.0,
+        "shard #6": 912.0,
+        "shard #7": 796.0
     }
 }
\ No newline at end of file