SF: Polish Fps class

For consistent comparison (which will later be changed to check ULP
distance instead of the magnitude-dependent threshold), express the
inequality operators in terms of equality, and avoid hashing floats.

Add Hz literals and (namespaced) operators.

Bug: 129481165
Bug: 185535769
Test: libsurfaceflinger_unittest
Test: dumpsys SurfaceFlinger --vsync
Change-Id: I79be5d2dd031218c4054774d2645efb337211538
diff --git a/services/surfaceflinger/tests/unittests/LayerInfoTest.cpp b/services/surfaceflinger/tests/unittests/LayerInfoTest.cpp
index d6ce5e2..f25994e 100644
--- a/services/surfaceflinger/tests/unittests/LayerInfoTest.cpp
+++ b/services/surfaceflinger/tests/unittests/LayerInfoTest.cpp
@@ -20,6 +20,7 @@
 #include <gtest/gtest.h>
 
 #include "Fps.h"
+#include "FpsOps.h"
 #include "Scheduler/LayerHistory.h"
 #include "Scheduler/LayerInfo.h"
 
@@ -47,7 +48,7 @@
 
 TEST_F(LayerInfoTest, prefersPresentTime) {
     std::deque<FrameTimeData> frameTimes;
-    constexpr auto kExpectedFps = Fps(50.0f);
+    constexpr auto kExpectedFps = 50_Hz;
     constexpr auto kPeriod = kExpectedFps.getPeriodNsecs();
     constexpr int kNumFrames = 10;
     for (int i = 1; i <= kNumFrames; i++) {
@@ -58,14 +59,12 @@
     setFrameTimes(frameTimes);
     const auto averageFrameTime = calculateAverageFrameTime();
     ASSERT_TRUE(averageFrameTime.has_value());
-    const auto averageFps = Fps::fromPeriodNsecs(*averageFrameTime);
-    ASSERT_TRUE(kExpectedFps.equalsWithMargin(averageFps))
-            << "Expected " << averageFps << " to be equal to " << kExpectedFps;
+    ASSERT_EQ(kExpectedFps, Fps::fromPeriodNsecs(*averageFrameTime));
 }
 
 TEST_F(LayerInfoTest, fallbacksToQueueTimeIfNoPresentTime) {
     std::deque<FrameTimeData> frameTimes;
-    constexpr auto kExpectedFps = Fps(50.0f);
+    constexpr auto kExpectedFps = 50_Hz;
     constexpr auto kPeriod = kExpectedFps.getPeriodNsecs();
     constexpr int kNumFrames = 10;
     for (int i = 1; i <= kNumFrames; i++) {
@@ -74,17 +73,15 @@
                                            .pendingModeChange = false});
     }
     setFrameTimes(frameTimes);
-    setLastRefreshRate(Fps(20.0f)); // Set to some valid value
+    setLastRefreshRate(20_Hz); // Set to some valid value.
     const auto averageFrameTime = calculateAverageFrameTime();
     ASSERT_TRUE(averageFrameTime.has_value());
-    const auto averageFps = Fps::fromPeriodNsecs(*averageFrameTime);
-    ASSERT_TRUE(kExpectedFps.equalsWithMargin(averageFps))
-            << "Expected " << averageFps << " to be equal to " << kExpectedFps;
+    ASSERT_EQ(kExpectedFps, Fps::fromPeriodNsecs(*averageFrameTime));
 }
 
 TEST_F(LayerInfoTest, returnsNulloptIfThereWasConfigChange) {
     std::deque<FrameTimeData> frameTimesWithoutConfigChange;
-    const auto period = Fps(50.0f).getPeriodNsecs();
+    const auto period = (50_Hz).getPeriodNsecs();
     constexpr int kNumFrames = 10;
     for (int i = 1; i <= kNumFrames; i++) {
         frameTimesWithoutConfigChange.push_back(FrameTimeData{.presentTime = period * i,
@@ -124,9 +121,9 @@
 // Make sure that this doesn't influence the calculated average FPS.
 TEST_F(LayerInfoTest, ignoresSmallPeriods) {
     std::deque<FrameTimeData> frameTimes;
-    constexpr auto kExpectedFps = Fps(50.0f);
+    constexpr auto kExpectedFps = 50_Hz;
     constexpr auto kExpectedPeriod = kExpectedFps.getPeriodNsecs();
-    constexpr auto kSmallPeriod = Fps(250.0f).getPeriodNsecs();
+    constexpr auto kSmallPeriod = (250_Hz).getPeriodNsecs();
     constexpr int kNumIterations = 10;
     for (int i = 1; i <= kNumIterations; i++) {
         frameTimes.push_back(FrameTimeData{.presentTime = kExpectedPeriod * i,
@@ -141,18 +138,16 @@
     setFrameTimes(frameTimes);
     const auto averageFrameTime = calculateAverageFrameTime();
     ASSERT_TRUE(averageFrameTime.has_value());
-    const auto averageFps = Fps::fromPeriodNsecs(*averageFrameTime);
-    ASSERT_TRUE(kExpectedFps.equalsWithMargin(averageFps))
-            << "Expected " << averageFps << " to be equal to " << kExpectedFps;
+    ASSERT_EQ(kExpectedFps, Fps::fromPeriodNsecs(*averageFrameTime));
 }
 
 // There may be a big period of time between two frames. Make sure that
 // this doesn't influence the calculated average FPS.
 TEST_F(LayerInfoTest, ignoresLargePeriods) {
     std::deque<FrameTimeData> frameTimes;
-    constexpr auto kExpectedFps = Fps(50.0f);
+    constexpr auto kExpectedFps = 50_Hz;
     constexpr auto kExpectedPeriod = kExpectedFps.getPeriodNsecs();
-    constexpr auto kLargePeriod = Fps(9.0f).getPeriodNsecs();
+    constexpr auto kLargePeriod = (9_Hz).getPeriodNsecs();
 
     auto record = [&](nsecs_t time) {
         frameTimes.push_back(
@@ -172,9 +167,7 @@
     setFrameTimes(frameTimes);
     const auto averageFrameTime = calculateAverageFrameTime();
     ASSERT_TRUE(averageFrameTime.has_value());
-    const auto averageFps = Fps::fromPeriodNsecs(*averageFrameTime);
-    ASSERT_TRUE(kExpectedFps.equalsWithMargin(averageFps))
-            << "Expected " << averageFps << " to be equal to " << kExpectedFps;
+    ASSERT_EQ(kExpectedFps, Fps::fromPeriodNsecs(*averageFrameTime));
 }
 
 } // namespace