Misc. small cleanups.

* Better param names
* Avoid using negative values for (bogus) placeholder channel counts (mostly in tests).  Since channels will be changing to size_t, negative values will be illegal; it's sufficient to use 0 in these cases.
* Use arraysize()
* Use size_t for counting frames, samples, blocks, buffers, and bytes -- most of these are already size_t in most places, this just fixes some stragglers
* reinterpret_cast<int64_t>(void*) is not necessarily safe; use uintptr_t instead
* Remove unnecessary code, e.g. dead code, needlessly long/repetitive code, or function overrides that exactly match the base definition
* Fix indenting
* Use uint32_t for timestamps (matching how it's already a uint32_t in most places)
* Spelling
* RTC_CHECK_EQ(expected, actual)
* Rewrap
* Use .empty()
* Be more pedantic about matching int/int32_t/
* Remove pointless consts on input parameters to functions
* Add missing sanity checks

All this was found in the course of constructing https://codereview.webrtc.org/1316523002/ , and is being landed separately first.

BUG=none
TEST=none

Review URL: https://codereview.webrtc.org/1534193008

Cr-Commit-Position: refs/heads/master@{#11191}

webrtc/system_wrappers/include/aligned_array.h

@@ -20,16 +20,15 @@ namespace webrtc {
 // aligned to the given byte alignment.
 template<typename T> class AlignedArray {
  public:
-  AlignedArray(int rows, size_t cols, int alignment)
+  AlignedArray(int rows, size_t cols, size_t alignment)
       : rows_(rows),
-        cols_(cols),
-        alignment_(alignment) {
-    RTC_CHECK_GT(alignment_, 0);
+        cols_(cols) {
+    RTC_CHECK_GT(alignment, 0u);
     head_row_ = static_cast<T**>(AlignedMalloc(rows_ * sizeof(*head_row_),
-                                               alignment_));
+                                               alignment));
     for (int i = 0; i < rows_; ++i) {
       head_row_[i] = static_cast<T*>(AlignedMalloc(cols_ * sizeof(**head_row_),
-                                                   alignment_));
+                                                   alignment));
     }
   }
 
@@ -79,7 +78,6 @@ template<typename T> class AlignedArray {
  private:
   int rows_;
   size_t cols_;
-  int alignment_;
   T** head_row_;
 };