aaudio: fix detection of input overflows

Was incorrectly looking at the buffer size instead of the buffer
capacity.

Test: OboeTester ECHO INPUT to OUTPUT
Test: set Input margin to 4
Test: XRun# for input should stay at zero
Bug: 141700208
Change-Id: I21ecdac19f5361a1b33f4dc2aaec170de9e28fc6
diff --git a/media/libaaudio/src/client/AudioStreamInternalCapture.cpp b/media/libaaudio/src/client/AudioStreamInternalCapture.cpp
index 366cc87..9684ee4 100644
--- a/media/libaaudio/src/client/AudioStreamInternalCapture.cpp
+++ b/media/libaaudio/src/client/AudioStreamInternalCapture.cpp
@@ -106,9 +106,10 @@
         mNeedCatchUp.acknowledge();
     }
 
-    // If the write index passed the read index then consider it an overrun.
+    // If the capture buffer is full beyond capacity then consider it an overrun.
     // For shared streams, the xRunCount is passed up from the service.
-    if (mAudioEndpoint.isFreeRunning() && mAudioEndpoint.getEmptyFramesAvailable() < 0) {
+    if (mAudioEndpoint.isFreeRunning()
+        && mAudioEndpoint.getFullFramesAvailable() > mAudioEndpoint.getBufferCapacityInFrames()) {
         mXRunCount++;
         if (ATRACE_ENABLED()) {
             ATRACE_INT("aaOverRuns", mXRunCount);