Revert "[battery] Add ResourceCoalitionMacTest.Busy."

This reverts commit 856342886a.

Reason for revert: failing on Mac10.13 Tests:
https://ci.chromium.org/ui/p/chromium/builders/ci/Mac10.13%20Tests/47610/overview

Summary:
[ RUN      ] ResourceCoalitionMacTest.Busy
../../components/power_metrics/resource_coalition_mac_unittest.mm:99: Failure
Expected: (end->cpu_instructions) > (begin->cpu_instructions), actual: 0 vs 0
Stack trace:
0   components_unittests                0x000000010b1da1e6 power_metrics::ResourceCoalitionMacTest_Busy_Test::TestBody() + 1014

../../components/power_metrics/resource_coalition_mac_unittest.mm💯 Failure
Expected: (end->cpu_cycles) > (begin->cpu_cycles), actual: 0 vs 0
Stack trace:
0   components_unittests                0x000000010b1da2d5 power_metrics::ResourceCoalitionMacTest_Busy_Test::TestBody() + 1253

[  FAILED  ] ResourceCoalitionMacTest.Busy (1113 ms)

Original change's description:
> [battery] Add ResourceCoalitionMacTest.Busy.
>
> This test verifies that CPU instructions, CPU cycles and CPU time
> reported by `GetCoalitionResourceUsage` increase after burning CPU.
> This is a basic expectations for `GetCoalitionResourceUsage` so it
> should be tested from //components/power_metrics/. In an upcoming
> CL, this will allow removing
> //chrome/browser/performance_monitor/resource_coalition_mac_unittest.mm
> without losing tests.
>
> Bug: 1293465
> Change-Id: I7232bd6b67406600b9fc89b7f7f80ad8db47c5f1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3437567
> Reviewed-by: Patrick Monette <pmonette@chromium.org>
> Commit-Queue: Francois Pierre Doray <fdoray@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#967015}

Bug: 1293465
Change-Id: Iea672af3c27d0484b75832f820f7e4a75c2cd4e2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3440125
Auto-Submit: Olga Sharonova <olka@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Olga Sharonova <olka@google.com>
Commit-Queue: Olga Sharonova <olka@chromium.org>
Cr-Commit-Position: refs/heads/main@{#967154}

components/power_metrics/resource_coalition_mac_unittest.mm

@@ -4,7 +4,6 @@
 
 #include "components/power_metrics/resource_coalition_mac.h"
 
-#include "base/rand_util.h"
 #include "components/power_metrics/energy_impact_mac.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
@@ -70,37 +69,8 @@ coalition_resource_usage GetTestCoalitionResourceUsage(uint32_t increment) {
   return ret;
 }
 
-void BurnCPU() {
-  base::TimeTicks begin = base::TimeTicks::Now();
-  constexpr base::TimeDelta busy_time = base::Seconds(1);
-  [[maybe_unused]] volatile double number = 1;
-  while (base::TimeTicks::Now() < (begin + busy_time)) {
-    for (int i = 0; i < 10000; ++i)
-      number *= base::RandDouble();
-  }
-}
-
 }  // namespace
 
-TEST(ResourceCoalitionMacTest, Busy) {
-  absl::optional<uint64_t> coalition_id =
-      GetProcessCoalitionId(base::GetCurrentProcId());
-  ASSERT_TRUE(coalition_id.has_value());
-
-  std::unique_ptr<coalition_resource_usage> begin =
-      GetCoalitionResourceUsage(coalition_id.value());
-  BurnCPU();
-  std::unique_ptr<coalition_resource_usage> end =
-      GetCoalitionResourceUsage(coalition_id.value());
-
-  ASSERT_TRUE(begin);
-  ASSERT_TRUE(end);
-
-  EXPECT_GT(end->cpu_instructions, begin->cpu_instructions);
-  EXPECT_GT(end->cpu_cycles, begin->cpu_cycles);
-  EXPECT_GT(end->cpu_time, begin->cpu_time);
-}
-
 TEST(ResourceCoalitionMacTest, Difference) {
   coalition_resource_usage left =
       GetTestCoalitionResourceUsage(/* increment= */ 1);