This CL fixes an overcite with the AVX2 support CL previously
merged (Change-Id: Idc03f3fca4bf2d0afd33631ea1d3caf8fc34ec29) that
prevented runtime execution of AVX2 code in WebM. 

Background:
Starting with the Sandybridge processor, the CPUID instruction was
enhanced to add various extended feature flag enumeration leaves.
Reading these leaves requires an additional input value for the CPUID
instruction which is stored in ECX. This change adds this second input
value for all ARCH_X86 and ARCH_x86_64 targets to the CPUID macros,
allowing checks of EBX bit 5 for AVX2 support. This capability will be
required moving forward to check for future processor features.

Change-Id: Ie9d872bc9ff68dad4b6578e4544e4dfd0ae26c36

Change-Id: I00a5203c8ed76c184d936fccf93d76e7c06773d3

In commit "3d50da53", the stack
pointer was modified while aligning the stack, and it needed to
be pop out at the end.

Change-Id: I062971e195f1f2ab9d0ab5fb84dcf215a0fcaa67

Patch in https://gerrit.chromium.org/gerrit/#/c/41176/
was merged into repository by mistake.

Change-Id: I235c71af26bb2d72698c8aac2301e5a7e9c5f960

There are many places in handle_inter_mode that need to restore the
dst buffer pointers, due to buffer pointer swap and early rd search
breakout. This commit wraps these operations into an inline function
for clean-up.

Change-Id: I0462e8c41c8bc3cd8db07395489cac03d8e5be54

Change-Id: I473947b5ca70b7a81151926284bff86f8555492a

This patch fixed issue 661: "Decoder produces mismatched outputs
with ssse3 enabled and disabled." In sub-pixel filters, a pixel
value was multiplied by a filter coefficient, and the results
were added up. The order of adding up these multiplications had to
be arranged carefully to prevent incorrect overflowing.

Change-Id: Id08af4200fea9e1b896fc40157b8651c2c7e80f2

Change-Id: Ifad4b0e6355ce49fcc6f470becc080e8069452ee

As it is used in encoder only.

Change-Id: I5f2a8abbe72bb18cbf6ce36a3dc7e132aeae8ec2

Change-Id: Ic316d3374ff9a2b43897272260947d56765a0fdd

Change-Id: I64b189dfeee1cf3e90134a1a93497072f3361e5e

Change-Id: I6f6ba91b1b8b280902b171472314d665aa0baf0b

Reversing bit order of partition_context_lookup, and modifying accordingly
update_partition_context() and partition_plane_context().

Change-Id: I64a11f1a94962a3bf217de2f50698cb781db71a5

The bug was introduced in 00a35aab. The reading of raw yuv input frame
was off by 4 bytes.

Change-Id: I6923ea5528aa529a47a06b64adca8f94847f19a6

- Move it to webmdec.c and webmdec.h.
- Also, tidy up obvious style nits in the vicinity of code I was
  already touching.

Change-Id: Ie2898d06e73c1e9030d9c8d465b73ee7edc3c02a

There is no need to use that function, it is much clear to pass offset
directly to the buffer.

Change-Id: I9026cb0c5094c46f97df5d7f7daeb952f2843b24

Change-Id: I23fea0a2e85be8373600e3e2dae98d36acde389c

This rebase is a better implementation of the previous ones.

Modifications are done to reduce the total clock cycle.
Speedup: 1.341
Compiled with -O3
Tested with: park_joy_420_720p50.y4m

Change-Id: I940eaf283f60597ca0d9d2e13d518878d55ff02d

Change-Id: I568f5e2d4ef2f2affe013ba1691ffb546f1fe8c6

Change-Id: Id578a5fe2039631cefd82dc2ef98cc62683194c3