Revert "Use the latest temperature read as base for headroom calculation"

This reverts commit 436e7d8bc035b11a6627cd82df3856c5f15371ab.

Reason for revert: <Dorid monitor: Likely culprit for b/346904307  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.>

Change-Id: Ife94d7148df3d47634c97564f81171059c82df04
diff --git a/services/core/java/com/android/server/power/ThermalManagerService.java b/services/core/java/com/android/server/power/ThermalManagerService.java
index 0052d4f..5360788 100644
--- a/services/core/java/com/android/server/power/ThermalManagerService.java
+++ b/services/core/java/com/android/server/power/ThermalManagerService.java
@@ -1709,7 +1709,7 @@
                     ArrayList<Sample> samples = mSamples.computeIfAbsent(temperature.getName(),
                             k -> new ArrayList<>(RING_BUFFER_SIZE));
                     if (samples.size() == RING_BUFFER_SIZE) {
-                        samples.removeFirst();
+                        samples.remove(0);
                     }
                     samples.add(new Sample(now, temperature.getValue()));
                 }
@@ -1806,7 +1806,7 @@
                         continue;
                     }
 
-                    float currentTemperature = samples.getLast().temperature;
+                    float currentTemperature = samples.get(0).temperature;
 
                     if (samples.size() < MINIMUM_SAMPLE_COUNT) {
                         // Don't try to forecast, just use the latest one we have
diff --git a/services/tests/servicestests/src/com/android/server/power/ThermalManagerServiceTest.java b/services/tests/servicestests/src/com/android/server/power/ThermalManagerServiceTest.java
index 6d79ae4..32bbc7a 100644
--- a/services/tests/servicestests/src/com/android/server/power/ThermalManagerServiceTest.java
+++ b/services/tests/servicestests/src/com/android/server/power/ThermalManagerServiceTest.java
@@ -551,7 +551,7 @@
 
         // Add some time-series data
         for (int i = 1; i < 20; ++i) {
-            samples.add(watcher.createSampleForTesting(1000 * i, 25.0f + 0.5f * i));
+            samples.add(0, watcher.createSampleForTesting(1000 * i, 25.0f + 0.5f * i));
         }
 
         // Now the forecast should vary depending on how far ahead we are trying to predict