Vulkan: Free pool allocation leak with graph disabled.

Our secondary command buffer pools were leaking memory every submit.
This change pops the secondary command buffer pool allocator scope
after commands are flushed during a submit.

Fixes the memory leak observable on any Vulkan application.

Bug: angleproject:4029
Bug: angleproject:4403
Change-Id: I3d0f8d53456336ef0b03c6d37425fb76c88d1551
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2057349
Reviewed-by: Jamie Madill <[email protected]>
Commit-Queue: Jamie Madill <[email protected]>

Author: null77

src/libANGLE/renderer/vulkan/ContextVk.cpp

@@ -721,6 +721,8 @@ angle::Result ContextVk::initialize()
 
     if (!commandGraphEnabled())
     {
+        // Push a scope in the pool allocator so we can easily reinitialize on flush.
+        mPoolAllocator.push();
         mOutsideRenderPassCommands.getCommandBuffer().initialize(&mPoolAllocator);
         mRenderPassCommands.initialize(&mPoolAllocator);
         ANGLE_TRY(startPrimaryCommandBuffer());
@@ -3698,6 +3700,13 @@ angle::Result ContextVk::flushImpl(const vk::Semaphore *signalSemaphore)
     {
         mOutsideRenderPassCommands.flushToPrimary(&mPrimaryCommands);
         ANGLE_TRY(endRenderPass());
+
+        // Free secondary command pool allocations and restart command buffers with the new page.
+        mPoolAllocator.pop();
+        mPoolAllocator.push();
+        mOutsideRenderPassCommands.reset();
+        mRenderPassCommands.reset();
+
         ANGLE_VK_TRY(this, mPrimaryCommands.end());
 
         Serial serial = getCurrentQueueSerial();