Return error when error occurs in buffer allocation.

Previously, the allocate buffer does not return error if it runs out of
memory. This change adds the error in returned status.

Test: buffer_hub_queue-test passes on Vega on oc-dr1-daydream-dev
branch.
Test: build and visually check on Vega on oc-dr1-daydream-dev branch.
Test: buffer_hub_queue-test passes on Marlin on master branch.

Change-Id: Ie226e506ff47d122cd4eef6071b44abedcd4be56
diff --git a/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp b/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp
index 1f2c517..44276ba 100644
--- a/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp
+++ b/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp
@@ -440,6 +440,10 @@
 Status<std::vector<size_t>> ProducerQueue::AllocateBuffers(
     uint32_t width, uint32_t height, uint32_t layer_count, uint32_t format,
     uint64_t usage, size_t buffer_count) {
+  if (buffer_count == 0) {
+    return {std::vector<size_t>()};
+  }
+
   if (capacity() + buffer_count > kMaxQueueCapacity) {
     ALOGE(
         "ProducerQueue::AllocateBuffers: queue is at capacity: %zu, cannot "
@@ -481,10 +485,13 @@
     }
   }
 
-  if (buffer_slots.size() == 0) {
-    // Error out if no buffer is allocated and improted.
-    ALOGE_IF(TRACE, "ProducerQueue::AllocateBuffers: no buffer allocated.");
-    ErrorStatus(ENOMEM);
+  if (buffer_slots.size() != buffer_count) {
+    // Error out if the count of imported buffer(s) is not correct.
+    ALOGE(
+        "ProducerQueue::AllocateBuffers: requested to import %zu "
+        "buffers, but actually imported %zu buffers.",
+        buffer_count, buffer_slots.size());
+    return ErrorStatus(ENOMEM);
   }
 
   return {std::move(buffer_slots)};
@@ -503,11 +510,6 @@
     return status.error_status();
   }
 
-  if (status.get().size() == 0) {
-    ALOGE_IF(TRACE, "ProducerQueue::AllocateBuffer: no buffer allocated.");
-    ErrorStatus(ENOMEM);
-  }
-
   return {status.get()[0]};
 }
 
diff --git a/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp b/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp
index 2975f56..046df54 100644
--- a/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp
+++ b/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp
@@ -562,6 +562,30 @@
   ASSERT_EQ(cs2, ps2);
 }
 
+TEST_F(BufferHubQueueTest, TestAllocateTwoBuffers) {
+  ASSERT_TRUE(CreateQueues(config_builder_.Build(), UsagePolicy{}));
+  ASSERT_EQ(producer_queue_->capacity(), 0);
+  auto status = producer_queue_->AllocateBuffers(
+      kBufferWidth, kBufferHeight, kBufferLayerCount, kBufferFormat,
+      kBufferUsage, /*buffer_count=*/2);
+  ASSERT_TRUE(status.ok());
+  std::vector<size_t> buffer_slots = status.take();
+  ASSERT_EQ(buffer_slots.size(), 2);
+  ASSERT_EQ(producer_queue_->capacity(), 2);
+}
+
+TEST_F(BufferHubQueueTest, TestAllocateZeroBuffers) {
+  ASSERT_TRUE(CreateQueues(config_builder_.Build(), UsagePolicy{}));
+  ASSERT_EQ(producer_queue_->capacity(), 0);
+  auto status = producer_queue_->AllocateBuffers(
+      kBufferWidth, kBufferHeight, kBufferLayerCount, kBufferFormat,
+      kBufferUsage, /*buffer_count=*/0);
+  ASSERT_TRUE(status.ok());
+  std::vector<size_t> buffer_slots = status.take();
+  ASSERT_EQ(buffer_slots.size(), 0);
+  ASSERT_EQ(producer_queue_->capacity(), 0);
+}
+
 TEST_F(BufferHubQueueTest, TestUsageSetMask) {
   const uint32_t set_mask = GRALLOC_USAGE_SW_WRITE_OFTEN;
   ASSERT_TRUE(